Idea Transcript
Strand: 8.2.6 Emphasis: Analog and digital signals Anticipated Time Required: LE 1 - 30 minutes LE 2 - 30-45 minutes LE 3 - 75-90 minutes LE 4 - 30-45 minutes Dominant CCC: Structure and function Dominant SEP: Engaging in argument from evidence; communicating information Management Strategies to support equitable access to content: My Favorite No (celebrating wrong answers and using them to develop deeper understanding) Shopping list: Learning episode 2: Tuning forks (an assortment of frequencies; ideally enough for each group of 3 students to have at least to forks, but 1 for each group or even one set to use for a class demonstration will work)
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Timeframe: 20 minutes
SEP: Arguing from evidence
CCC: Cause and effect; structure and function
CCC/SEP
Energy
Students model transmission of different signals.
What are students doing? (This should match your SEP!)
Dominant DCI
Some signals are more distorted than others during transmission.
What specific understandings should students get from this experience?
Science Experiences
Structure and function
Dominant CCC
How does a sound signal get from the source to the target? What could cause distortions in sound waves?
New questions students have to propel us to the next science experience.
Formative: Student explanations and supporting evidence of which signals to use in which situations can be used to assess their understanding of the different types of signals modeled by the class.
Assessment
Arguing from evidence; communicating information
Dominant SEP
NGSS Evidence Statements MS-PS4-3: https://www.nextgenscience.org/sites/default/files/evidence_statement/black_white/MS-PS43%20Evidence%20Statements%20June%202015%20asterisks.pdf
8.2.6: Obtain and evaluate information to communicate the claim that the structure of digital signals are a more reliable way to store or transmit information than analog signals. Emphasize the basic understanding that waves can be used for communication purposes. Examples could include using vinyl record vs. digital song files, film cameras vs. digital cameras, or alcohol thermometers vs. digital thermometers.
Student Performance Expectation:
Anchor Phenomenon: NASA has sent signals out into space, with important information that could be received by extraterrestrial life, if it exists. Big Question: What types of signals are best suited for storing and transmitting important information?
8.2.6 Digital versus Analog Signals Storyline
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Students send analog and digital signals, and compare the resulting information to the original information. They compare these signals to the signals modeled during the telephone game in the first lesson.
Students use observations from a tuning fork to create a model to show how sound waves transfer energy from one place to another.
Students read about the Timeframe: differences between analog 75-90 minutes and digital waves. They observe and compare analog and digital audio signals, and evaluate how well the integrity of the signals are maintained during storage and transmission.
SEP: Constructing explanations
CCC: Structure and function; cause and effect
Timeframe: 30 minutes
SEP: Developing and using models
CCC: Energy and matter; cause and effect
The structure of analog signals makes it possible to capture richer sounds, because all of the sound is recorded, but they take more space to store and can be
The structure of digital signals allows them to be stored in smaller spaces for longer times without becoming corrupt, but the sounds are somewhat simplified.
Digital signals only include a sample of the original sound energy.
Digital signals can be more easily transmitted without becoming distorted.
Analog signals are easily distorted, and become more distorted each time they are transmitted.
Sound energy is transferred through the air vis longitudinal waves (students do not need to know the term, but should understand the concept)
Which type of wave should we use to store and transmit signals?
How can we record and store these waves if we want to send a signal far away or to the future?
Formative: Student analogies of digital/analog signals and the signals sent during the telephone game should be used to assess their understanding of the benefits and drawbacks of each type of signal (digital and analog).
Formative: Student models of sound waves are used to assess their understanding of how sound energy is transferred.
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Students gather/review Digital and analog signals both information about digital and have benefits and drawbacks. analog signals from a short video, and then use evidence SEP: to support a claim that Engage in answers the question, “Should argument we use analog or digital from evidence signals to store and transmit important information for the Timeframe: future?” 30-45 minutes
CCC: structure and function
corrupted (by heat, background noise during recording, etc.). Summative-: Students should write an argumentative essay using evidence to support the claim that either analog or digital is better for storing and transmitting signals based on structure and function. Use the rubric to identify excellent student papers.
8.2.6 Learning Episode 1
Student Science Performance Topic: Digital vs. Analog
Title: Telephone Game Activity
Overarching Performance Expectations (Standard) from State Standards or NGSS: Obtain and evaluate information to communicate the claim that the structure of digital signals are a more reliable way to store or transmit information than analog signals. Emphasize the basic understanding that waves can be used for communication purposes. Examples could include using vinyl record vs. digital song files, film cameras vs. digital cameras, or alcohol thermometers vs. digital thermometers. Lesson Performance Expectations: Students should model transmission of different types of signals, and should use evidence to explain how the structure of the signals affect their functions CCC: Structure and function; cause and effect SEP: Asking Questions; developing models Students Will. . . To Construct Meaning Engage with a phenomenon: Sometimes information is changed when it is transmitted from a source to a target. Starter: Signals are used to transmit information from one place to another, or from one time to sometime in the future. Complete the 3-2-1 activity in your lab book: ● 3: types of signals that could be used to transmit information ● 2: things that all signals have in common ● 1: question that you have about signals
Gather: As a class, you will be modeling two different types of signals. We’re going to compare the information that gets sent to the information that is received, and decide which type of signal would be better for transmitting information. Follow your teacher’s instructions for modeling the transmission of signals.
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Teacher Will. . . To Support Students Give the students the starter. As they work on the questions, circulate through the room and make note of what students are writing. If there are specific ideas that you want students to share during the class discussion, quietly tell the students you’ll be calling on them during the discussion so they are prepared. After students complete the starter, facilitate a class discussion. Some ideas that you should help students bring out: ● Signals could be visual (waving at a friend, signaling with mirrors or smoke, etc.), auditory (whales singing to each other, yelling or laughing, etc.), etc. ● All signals contain information and have a starting point (source) and a target; the information signals contain could be very different (How is the information communicated by a smile different from the information communicated by someone poking you? What about the difference in information between a wave or rolling your eyes?) Allow students to share some of their questions about signals, but at this point, don’t answer any of them. Tell students that we will be trying to figure out answers to some of their questions over the course of this unit. Post the questions and refer to them throughout the unit when appropriate. For the first signal: You will be playing the telephone game. Prepare a card that is labeled “signal 1” and write the sentence you would like to communicate on it. Have students stand in a line or a circle. The last student has a blank card labeled “signal 1.” Show your card with the sentence on it to the first student. She should then whisper the message to the next student, who whispers it to the next student and so forth until the last student receives the message. When the last student receives the message, she records it on the card and hands the
card to you. For the second signal: Prepare a card that has a series of dots and is labeled “signal 2.” Each student should have a blank card and a pencil. Students should be standing in a line, so they are facing the back of the person that they will be transmitting the signal to. Hand your card to the first student. She will then tap the shoulder of the next student, and show him the card. After looking at the card, he will turn back around, record the message on his own blank card, and tap the shoulder of the next student. This process is repeated until the last student has recorded the message. Collect the card from the last student, label it “signal 2,” and allow everyone to return to their seats. Note: if you have a large class, consider breaking them into two groups for this activity to save time. You can start the message at the beginning of each line and collect the ending cards from each line. Make sure that you use the same number of groups for both signals. Reason: With your group, discuss which signal would be better for transmitting information. To record your ideas, make a table in your lab book and record the pros and cons of each signal we modeled.
Once students return to their seats, display the starting and ending messages from each signal. Place students in small groups to discuss the differences in the two signals. As they discuss and record their ideas, circulate through the class and listen to what they are saying. Facilitate a class discussion to allow students to explain the benefits and drawbacks of each type of signal. Some ideas students may have: ● Signal 1 con = message was distorted/information was changed during the signal transmission ● Signal 2 con = dots don’t really mean anything/no useful information was transmitted ● Signal 2 pro = message wasn’t as distorted At some point, help focus student attention on the structure of the signals. For example, signal 1 contained a lot of information, but was easily distorted. Use questions to bring out the fact that signal 2 would need to be translated into something meaningful. You could give the example of Morse code, where letters are translated to symbols at the source (dashes and dots), and the target would have to translate the symbols back into letters to make the signal meaningful. The simple structure of the signal make it easier to transmit without distortion, but the information was not necessarily useful. Later in the unit, students will need to understand that digital signals need to be turned back into analog signals for us to hear and make sense of them. Helping students understand that translating information to a different form that can be transmitted with fewer distortions and then translated back into something meaningful will set up a good foundation for later lessons.
Communicate: Determine which of the signals you would want to use for each of the following. In your lab book, record which signal you would use and why: ● Send a short message during a natural disaster E. Harward
Have students determine which signal would be better in each situation and record their ideas in their lab books or use as an exit ticket. There is not a correct answer to which signal is better, but students should be able to explain why they would use one signal over the other.
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Tell your friend why you didn’t go to her birthday party When students are done, introduce the anchor phenomenon by briefly telling them that different organizations, including NASA, have sent signals out into space to transmit information to other lifeforms, if they exist. During this unit, students will be working to determine what types of signals would be best suited for storing and transmitting important information.
Assessment of Student Learning Student responses should include evidence to support their choice of which signal is better in each situation; examples include: ● “Signal 2 would be better in a natural disaster because there could be large consequences if the information being transmitted was changed; for example, if you were trying to communicate your location to a rescuer and the information was changed, they wouldn’t be able to find you.” ● “Signal 1 would be better for talking to your friend, because he wouldn’t have to translate the dots. If there was a lot of information because you had a long excuse, your friend would have to translate a lot of dots. Plus, if you are telling your friend directly, the information doesn’t have as much chance to become distorted.”
Telephone Game
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Start and End Card Examples
Signal 1 Source
Signal 1 Target
The funny bunny hid the colored candy in the car.
Signal 2 Source
⚫⚫⚫
Signal 2 Target
⚫
Name _______________________________________________________________ period _______
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3-2-1 Starter
Signals
3 types of signals that could be used to transmit information: ★ ★ ★ 2 things that all signals have in common: ★ ★ 1 question that you have about signals: ★
Name _______________________________________________________________ period _______ E. Harward
Signals Exit Ticket Which signaling method would you want to use in each of the following situations? Why?
Situation
Which signal would you use?
Explain your answer.
You need to send a short message during a natural disaster
You need to tell your friend why you didn’t go to his birthday party
Name __________________________________________________________________ period _________ Signals With your group, discuss the benefits and drawbacks of each of the signals we modeled in class. Record your ideas in the table below. Pros
Signal 1
Signal 2
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Cons
8.2.6 Learning Episode 2
Student Science Performance Topic: Digital vs. Analog
Title: Modeling a Wave
Overarching Performance Expectations (Standard) from State Standards or NGSS: Obtain and evaluate information to communicate the claim that the structure of digital signals are a more reliable way to store or transmit information than analog signals. Emphasize the basic understanding that waves can be used for communication purposes. Examples could include using vinyl record vs. digital song files, film cameras vs. digital cameras, or alcohol thermometers vs. digital thermometers. Lesson Performance Expectations: Students will use observations to develop a model to show how sound energy is transferred from the source to the target. CCC: Energy and matter; cause and effect SEP: Developing and using models Students Will. . . To Construct Meaning Engage with a Phenomenon: When you hit a tuning fork against the table, the forks vibrate and it makes a noise. Gather: With your group, investigate and observe the tuning forks. In your lab book, record your ideas about: ● How are the tuning forks transmitting signals? ● What information is transmitted in the signals coming from the tuning forks? ● Are the tuning forks transmitting the same information? Is there a way to change the information being transmitted by the tuning forks? Reason: You will be developing a model to show how a signal was sent from the tuning fork to your ear. To do this, start by defining the system: ● Where are the system boundaries? For example, is the system just the fork and the air directly around the fork? Does it include the entire school? ● What are the parts of the system? For example, is the hand holding the tuning fork part of the system? What about your ear? What about your hair? Is there any empty space in the system? ● Describe the function of the different parts of the system. How is the structure of each part related to its E. Harward
Teacher Will. . . To Support Students Note: This is a great episode to find ways to connect to previous storylines regarding energy transfer and movement of matter. Ideally, you could provide each group of 3 students with 2-3 tuning forks to play with. If this is not practical for your budget, consider giving each group one tuning fork to start with and allowing them to trade with other groups throughout the activity. As a last resort, you could demonstrate a few tuning forks for the class to observe. Provide a sheet with the investigation questions or display the questions on the board. As students investigate and discuss with their groups, circulate through the class and use questions to help students clarify their ideas.
If your students are familiar with developing models, you can quickly remind them of the factors they need to consider (defining the system, including energy flow, and thinking about how to actually represent these ideas). If your students are not as practiced at making models or need extra scaffolding, take a few minutes on each step. Review systems, and allow students a few minutes to write down their system boundaries and the parts of the system before moving on to energy. After reviewing systems, energy and features that models can include, allow students time to revise their models. As they do this, circulate through the room. If there are students who need additional guidance, use questions to help them think through the processes happening in the system and how they want to represent these processes. Example questions: ● “What was going on with your ear that allowed you to hear the signal? Did the tuning fork have to touch your ear?” ● “What fills the space between the fork and your ear? Does
function? For example, what is the structure of the tuning fork? What is its function? How are the structure and function related? Now think about the energy in the system: ● What forms of energy are present in the system? ● What is the energy doing? Is it stored? Is it flowing? ● Is the energy causing any changes to the system? If so, what are they? Now revise your model to show how a signal is sent (and received!) in the system. You may want to think about what type of features will be useful for your model: ● Zoom-in boxes? ● Before-during-after diagrams? ● Written descriptions/explanations? ● Key?
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this play a role in transmitting the signal?” “Did the signal only go to your ear, or did it hit other targets as well? How can you show this in your model?” “What could you actually see happening? What are parts of the system that you didn’t actually see, but are making a guess about what was happening?” “How does the structure of _____ affect its function?” “What would happen if the tuning fork’s structure was different? What if it was made out of glass? Could it still have the same function? Why or why not?”
Allow students a few minutes to share their models with their partners. If needed, model what their discussion should look and sound like, and consider setting a timer so students know when to switch roles. As students discuss, circulate through the room and listen to their ideas. Identify students who have ideas that will help facilitate a class discussion, specifically listening for ideas about how the sound energy is able to move through the air. Selecting students who have both correct and incorrect ideas about this to participate in the class discussion will provide an opportunity for all students to think about how the sound travels through the air. Management Strategy: Eavesdropping on student discussions is an important skill! As you listen to students and identify ideas that will help facilitate the class discussion, tell the students that you will be calling on them during the discussion. For many students, knowing when they will be called on and already having an idea prepared allows them to participate in the class discussion without as much anxiety. Also consider telling the student why you want him to share his idea: ● “I’ve never had a student come up with that idea! I’d love for everyone to hear it.” ● “You worded your idea so well. I want to make sure the rest of the students have a chance to write it down.” ● “You two have such different ideas, and you both made great arguments to support your ideas. I love the way you listened to each other, even though you don’t agree. I’m going to call on you first during the class discussion to share your ideas.”
During the class discussion, you are welcome to add notes to your model. You will be revising your modes, and can refer to the notes you take. After watching the sound wave simulation, revise your model. Make sure it shows how the sound energy travels through the air.
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Facilitate a class discussion to allow students to share their ideas. During the discussion, build a class model (or several, if needed) to show the students’ ideas of how sound travels through the air.
If the class understands how sound waves affect air molecules as they travel from the fork to your ear, allow students to revise their own models. If the class has come up with several ideas about how sound waves travel, use the “soundwaves” simulation at https://musiclab.chromeexperiments.com/Sound-Waves to allow
Communicate: Share one revision you made to your model with your partner. ● Show your partner the revision (“I added _____.” or “I changed _____.” or “I got rid of _____.”) ● Tell your partner why you made the revision (“Before I thought _____, but now I know _____, so I changed it to ______.” or “I realized my model didn’t show _____, so I _____.”
students to see how air molecules are affected as sound energy passes through them. At this point, do NOT click on the magnifying lense in the simulation! Although it lets you zoom-in and see the molecules better, it traces the path of a single molecule in a way that creates a transverse wave on the screen, and students could come away with the misconception that this is what sound waves look like as they travel through the air. After playing with the simulation (and discussing the observations that students make), allow the students time to revise their drawings. If needed, remind students that zoom-in boxes and before-during-after sequences might be useful in showing how the air molecules move as sound energy is transmitted through the air. Give students 1-2 minutes to share their revisions with their partner.
Assessment of Student Learnings Student models should be used to assess their understanding of how sound signals can be transported through the air from a source to their ear. Models should include: ● System parts/boundaries ● Representation of energy moving from the fork outward ● Representation of the effects on the air molecules as the sound waves pass through them (how the energy causes them to move) ● Zoom-in boxes, written descriptions, etc. that effectively communicate the student’s ideas. Example:
Name ______________________________________________________________ period _______
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Tuning Forks As you play with the tuning forks, record your observations and ideas about the following. You can use words and pictures to record your ideas.
How are the tuning forks transmitting signals?
What information is transmitted in the signals coming from the tuning forks?
Are all of the tuning forks transmitting the same information? Is there a way to change the information being transmitted by the tuning forks?
Before creating your model, write down your ideas about the following: What is the system? What are the system boundaries, and what are the parts of the system?
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What form(s) of energy are in the system? What is the energy doing? Is it stored? Is it causing changes?
What are some features that you could include to communicate your ideas?
8.2.6 Learning Episode 3 Student Science Performance Topic: Digital vs. Analog
Title: Analog and digital signals
Overarching Performance Expectations (Standard) from State Standards or NGSS: Obtain and evaluate information to communicate the claim that the structure of digital signals are a more reliable way to store or transmit information than analog signals. Emphasize the basic understanding that waves can be used for communication purposes. Examples could include using vinyl record vs. digital song files, film cameras vs. digital cameras, or alcohol thermometers vs. digital thermometers. Lesson Performance Expectations: Students analyze and interpret visual representations of sound waves, and use evidence gathered from reading to determine if the sound waves were transmitted using analog or digital technologies. CCC: Patterns; structure and function SEP: Analyzing and interpreting data; arguing from evidence Students Will. . . To Construct Meaning Engage with a phenomenon: Visual representations of sound waves show that some sound recordings change when repeatedly transmitted while other recordings do not.
Gather: You will be playing the telephone game again, but this time you will be using different signals.
After you play the game and listen to the final messages, respond to the following questions in your lab book: ● Compare this telephone game to the first one we played. What was the same? What was different? Which signals were analogous? ● What forms of energy were involved? Was the information passed from person to person in the type of sound wave we modeled last time with the tuning forks? If not, how was the information passed from person to person? E. Harward
Teacher Will. . . To Support Students Note: The opening activity requires students to have electronic devices that can record sounds; some students will also need to send texts or emails. If you choose to have students use their cell phones for the activity, consider putting them in groups so that those who do not have or do not want to use their phones for the activity are paired with someone who has a phone. Classroom chromebooks, tablets, etc. give every student equal access and are a great option for this; however, it might take longer for students to figure out how to send and receive the message. If at all possible, don’t skip this activity because it will be engaging to your students and set up a great foundation for the rest of the lesson. If you have time and resources, allow the students play the telephone game again, only this time use actual digital and analog signals (students do not need to know those terms at this point). Divide the class into two groups. Have one student from each group bring their phone or computer out in the hall with you. Each student should use the microphone on their computer to record the same message from you (say the message one time, with both students recording; you may want to check and make sure both students recorded the entire message). Return to the class with the students, and explain that they each have the same recording of a message from you on their phone/computer. One team has to actually play and re-record the message each time they pass it from one person to the next. The other team can send the audio file by email or text; they should not actually open the file and listen to it. After the message has been passed through each team, the whole class can listen to the final version of each message. After students have a chance to respond to the questions in their lab books, facilitate a short class discussion to allow them to share their ideas. At this point, don’t feed them information. Just listen and use what they are saying to assess their understanding of signals and sound waves, and also to identify misconceptions.
Individually, read the information regarding digital and analog signals. As you read, underline the pros and cons of digital signals and the pros and cons of analog signals. Make a small note next to each underlined statement to show what type of signal it is talking about and if you think it is a pro or a con.
Distribute the readings. As the students read, circulate through the room and observe the statements that they are underlining. Remind students to note if each statement is a pro or a con. Consider providing ELL/SPED students with an abbreviated version of the reading (included with the lesson materials). This video may also be used to help students differentiate between digital and analog; consider starting it at 0:12ish (a word that may offend some students is displayed at the beginning of the video): https://www.youtube.com/watch?v=btgAUdbj85E. If needed, use small group or a whole group discussion to let students share the pros and cons they found in the reading.
Reason: With your partner, determine which signal from the first telephone game was a model of digital signals and which was a model of analog signals. Also determine which signal from today’s telephone game was a digital signal and with was analog. Your answer should include information regarding the structure of the signals.
Tell students that during the first telephone activity, they modeled the transmission of digital and analog signals. During the telephone activity they did for this lesson, they actually used digital and analog transmissions. Tell students that their task is to use evidence from the reading to determine which signal was digital and which was analog (and which signal modeled digital and which modeled analog).
Record your ideas, and make sure you include evidence from the reading to support your answers! You are welcome to use words and pictures in your explanation.
As students work with their partners, circulate through the room and listen to their ideas. If needed, remind students that they need to record their own claim about how each signal was modeled, and include evidence. Use questions to help students clarify their ideas. Encourage students to look at the notes they made during the telephone activity. Listen for student ideas that will be helpful in facilitating the class discussion. Facilitate a short class discussion to allow students to share their claims and evidence. Evidences that students may use to support their claims: ● Digital signals must be converted from analog, then converted back to analog for us to hear them ● Analog signals contain more information than digital, because they contain all of the sounds and digital signals only contain samples ● Digital signals take up less storage space than analog signals
Look for patterns in the waves you see on the screen and the noises that produced the waves. What are the effects of: ● changing the volume of the sound? ● changing the pitch of the sound? ● singing, clapping your hands or whistling? ● one person talking vs. three people talking?
Introduce the students to the idea that we can use a tool called an oscilloscope to visualize sound waves. Two great simulators that you can demonstrate for the class (project your computer screen; your computer will need a microphone so students can record sounds): ● https://academo.org/demos/virtual-oscilloscope/ ● https://musiclab.chromeexperiments.com/Voice-Spinner (this allows you to see the sound waves and play them back at different speeds; students don’t need to understand how the frequency affects sound, but students will like playing around with it and will be able to see the visual representation of a sound wave) Record a few sounds as a class and reiterate that these are not actual sound waves, but are visual representations of the waves. If needed, remind students of the sound wave models they created, and point out the differences, including the way sound waves affect the air molecules and do not move in the up-and-down pattern of the waves in this simulations.
The pictures are visual representations of sound waves. The
Distribute the sound wave transmission pictures and allow students time with their partner to analyze and interpret the pictures. If individual accountability is
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original sound wave was transmitted five times using one type of technology. Then the original sound wave was transmitted five times using a different type of technology. With your partner, look at the visual representations of the waves, and predict which final transmission sounded most like the original. Be ready to explain and support your answer during the class discussion.
needed for a particular class, ask students to write down which signaling method maintained the integrity of the sound and include their evidence. Otherwise, have students discuss these ideas and be ready to share during the class discussion.
Communicate: Review the signal pictures. One transmission was digital and the other was analog. Which do you think was digital? Write your answer on your card, and include the evidence or reasoning you used to support your answer. When you finish, give your card to your teacher.
Distribute an index card or slip of paper to each student. Tell the students that the original signal was transmitted using digital technology and that the original was transmitted using analog technology. They must determine which signal was transmitted digitally. Students should write their answer, including their evidence/reasoning, on the slip of paper and hand it in. Once all responses have been collected, use the My Favorite No strategy to help students further analyze the question.
Facilitate a short class discussion to allow students to share their ideas. Before moving to the next section, ensure that students understand the difference between analog and digital signals, and that they understand the pros and cons of each. During the discussion, if students make claims that one signal was digital and the other was analog, don’t tell them if they are right or wrong, but do ask them to share their evidence and reasoning with the class.
Formative Assessment Strategy: My Favorite No from http://www.redesignu.org/design-lab/learning-activities/my-favorite-no **Although this strategy can be very effective for helping students develop deeper understanding of a concept and reinforce the idea that wrong answers are a part of learning, it can be ineffective if used in a class that does not have a “failing forward” culture! Be sensitive about how you use this strategy. If used frequently in the right climate, it can help establish norms of having wrong answers and then working to correct them. After collecting student responses, sort them into two piles: a “yes” pile that contains correct answers and a “no” pile that contains incorrect answers. Say “yes” and “no” as you do this so students can see how you are sorting the answers. As you sort the answers, look for common mistakes that students are making, or for answers that include misconceptions that will be useful in helping students analyze the concept. Select the “no” answer that will help facilitate a discussion that will allow students to come to a deeper understanding of the concept. In this case, the “no” answer might include the correct signal, but have incorrect evidence/reasoning to support it. Tell the class that this is your favorite no answer, and make it clear that this answer is incorrect. (Do not identify who wrote the answer!) Read the answer to the class and ask them to analyze it by: ● determining which parts of the answer are correct ● which parts are incorrect, what makes these parts incorrect, and what changes could be made to make the answer correct End on a positive note! Acknowledge that it can be difficult to have your wrong answer analyzed by the class, even when it is done anonymously and remind the students the importance of wrong answers.
Assessment of Student Learning Written responses and ideas shared during partner and class discussions should be used to assess how well students understand differences between analog and digital signals. Student responses should demonstrate that they understand: ● Digital signals are less likely to become corrupted with repeated transmission and can be stored in a smaller E. Harward
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space; to make a digital recording, only samples of the original soundwave are recorded Analog signals are more likely to become corrupted and take more space to store, but analog technologies record the complete soundwave
Digital and Analog Signals
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When analog technology is used to record a sound, every part of the sound wave is recorded. The recorded sound waves can be very complex, because the recording device records every sound that it picks up, even background noises that are traveling through the air. The pictures to the right are visual representations of sounds that were recorded using analog technology. These signals can be changed easily, because when the sound is transmitted and recorded, it is hard for every part of the wave to be recorded exactly the same each time. Any additional background noise could be recorded with it, changing the wave and the sound.
When sounds are recorded digitally, not every part of the sound wave is recorded. Instead, the recording device takes samples of the sound wave, and assigns it to be either “on” or “off.” The picture to the right shows the recording of a digital wave. One thing you might notice is that in the analog recording, the wave can have any value. There are points of the wave at 0.2, -1, 1.4, etc. If the wave is recorded digitally, there are only two values. The wave can either be at 0 or 1. Since there are only two options for any point on the wave, it is harder to make changes to the wave if the sound is transmitted. Since the wave retains the same values, the sound it encodes remains unchanged. To make a digital recording, the sound has to be translated into a simpler version. The information takes up less storage space and is less likely to get changed or altered. However, to be able to get any information from the signal, it must be converted back into an analog signal before being transmitted to your ears.
Digital and Analog Signals
These pictures shows sounds that were recorded with analog technology.
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These sound waves are complex. This makes it hard to keep the sound waves exactly the same when they are copied. If these sound waves are copied, there will probably be small changes to them. This will change the sounds.
This picture shows a sound that was recorded with digital technology. These waves are simpler. It is easier to copy these waves without changing them. This means that the waves can be copied or stored without changing the sound. Digital signals do not take as much space to store as analog signals. This is why you can store many songs in your phone or computer. Before you can listen to this sound, it must be changed from a digital wave to an analog wave.
Transmission A
Original sound wave
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Sound wave after being transmitted five times
Transmission B
Original sound wave
Sound wave after being transmitted five times
Name __________________________________________________________________ period ________ Digital and Analog Signals Which signal (1 or 2) from the telephone activity at the beginning of the unit modeled a digital signal? What evidence can you use to support your answer? Remember to discuss the structure of the signals!
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Which signal (1 or 2) from the telephone activity at the beginning of the unit modeled an analog signal? What evidence can you use to support your answer? Remember to discuss the structure of the signals!
Which final transmission (A or B) sounded more like the original? What evidence do you have to support your answer?
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8.2.6 Learning Episode 4
Student Science Performance Topic: Digital vs. Analog
Title: Which signal should we use?
Overarching Performance Expectations (Standard) from State Standards or NGSS: Obtain and evaluate information to communicate the claim that the structure of digital signals are a more reliable way to store or transmit information than analog signals. Emphasize the basic understanding that waves can be used for communication purposes. Examples could include using vinyl record vs. digital song files, film cameras vs. digital cameras, or alcohol thermometers vs. digital thermometers. Lesson Performance Expectations: Students will use evidence about the structure of digital and analog signals to support an argument about which type of signal we should use to store and transmit information. CCC: Structure and function SEP: Engage in argument based on evidence; communicate information Students Will. . . To Construct Meaning Engage with a Phenomenon: Digital recordings maintain the same structure when recorded and transmitted. Analog recordings capture the sound as it originally was, without altering the sound waves. Gather: You will be making a claim about digital and analog signals. If you feel like you need more time to make sense of this information, use the tools your teacher has provided.
Teacher Will. . . To Support Students Use the formative assessments you made during the previous lesson to determine how much additional information and sense-making opportunities your students need before they will be able to successfully make an argument regarding how we should store and transmit signals. If students need additional support, consider: ● Having them create a diagram to show how digital and analog signals are similar and different ● Allowing them to gather information about digital and analog signals from various sources, and recording information about the signals in a graphic organizer ● Developing a model to show what happens to the sound energy if they sing into their phone’s voice recorder, text the song to a friend, and the friend listens to it; students should show the difference between the analog waves and the digital waves Sources that might be helpful for students to continue gathering information: ● https://www.youtube.com/watch?v=btgAUdbj85E (same video link as the previous lesson; consider starting the video at 0:12 to avoid showing a word that could be offensive to some students) ● http://www.cyberphysics.co.uk/topics/waves/analogueanddigital.htm (fairly short and straight-forward article about digital and analog signals) ● https://www.cliffsnotes.com/cliffsnotes/subjects/math/what-s-the-differ ence-between-digital-and-analog (short article about digital and analog signals)
Reason: What are the pros and cons of sending all that information in analog form to a target far away and in the future? How does the structure of analog signals relate to the pros and cons on your lists? Record your ideas in your lab book.
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Introduce students to the golden record: NASA recorded sounds and images using analog technology and sent them into space on Voyager on what is called “the golden record.” A brief description of the record can be found at https://voyager.jpl.nasa.gov/spacecraft/goldenrec.html. You can listen to sounds from the golden record on soundcloud (if you do a search for “NASA
golden record” in https://soundcloud.com/, you’ll find several different playlists; here is one: https://soundcloud.com/nasa/sets/golden-record-sounds-of). Students may find it interesting that we’ve actually used analog technology to store and transmit information to a target far away and far into the future. Play some of the recordings for the students, and let them comment of the quality of the sounds and the possible benefits of sending signals into space in analog form.
Communicate: You will need to make a claim that answers the question, “What type of signal should we use to store and transmit important information?” ● ● ●
Record your claim. Record evidence to support your claim. Explain your reasoning; how does the evidence you listed support your claim?
Allow students time to record their pros and cons; consider asking students to do this in partners or small groups. It is important that they understand of the benefits and the drawbacks of using analog signals before they start on their final assessment. Consider giving students the choice to develop an explanatory model to communicate their claim, evidence and reasoning, or to use the traditional written form. The same rubric can be provided regardless of the format the student selects. Provide students with the question. Depending on the class, you may want to provide additional scaffolding by giving students a graphic organizer to record their claim, evidence and reasoning, and then allow them to use these notes on their final product. You could also consider walking through each piece with the class. To do this: ● Go over the question with the class. ● Remind students that the claim is a statement that answers the question, and give them a minute to write their claim. ● Remind students that evidence is the stuff we observe. If needed, provide an example piece of evidence, and then allow students time to record the evidence that supports their claim. Encourage students to look at their previous notes as they do this. ● Explain to students that their reasoning is where they explain how the evidence they listed supports the claim they made. Allow students to work on their reasoning. Remember that constructing their reasoning using evidence is hard for students and they need a lot of practice. If you have a large number of ELL/SPED or struggling students, of if the claim-evidence-reasoning process is new to your students, consider providing additional scaffolding. Some ideas are included in the teacher materials for this lesson. In this case, students are using the claim-evidence-reasoning model to generate notes they can use to produce either an argumentative essay or model to communicate their claim and support it with evidence.
Assessment of Student Learning Students pro/con lists should be used to formatively assess their understanding of the differences between analog and digital signals. Students should have a good grasp of these differences before they are asked to do the summative assessment. Student CERs should be used as a summative assessment; a suggested rubric is below. Although students can choose to claim that analog technologies are better for storing information, somewhere (either in their formative or summative assessments), they should recognize that information is less likely to become corrupted if stored digitally.
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Surpasses proficiency
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Student claim is relevant At least three pieces of relevant evidence are used to support the claim Explanation of how or why the evidence supports the claim is included and relevant Student ideas and understanding are communicated effectively (for example, symbols used in models are clear or written responses are structured in a way that makes the student explanation easy to follow) Counterclaims are included and addressed
Proficient
● ● ● ●
Student claim is relevant At least two pieces of relevant evidence are used to support the claim Explanation of how or why the evidence supports the claim is included and relevant Student ideas and understanding are communicated effectively (for example, symbols used in models are clear or written responses are structured in a way that makes the student explanation easy to follow)
Approaching proficiency
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Student claim is relevant At least one piece of relevant evidence are used to support the claim Explanation of how or why the evidence supports the claim is included; some pieces may be incomplete or irrelevant Student ideas and understanding are mostly communicated effectively; there may be some pieces that are hard to interpret or ambiguous
● Below proficiency
● ● ● ●
Student claim may be irrelevant or missing Evidence cited is not relevant Explanation of how or why the evidence supports the claim may be missing, incorrect or incomplete Student ideas and understanding are not communicated effectively; it may be hard to understand the student’s ideas
Examples of proficient products: We should use digital technology to store and transmit signals, especially if we are trying to store or send important information. Digital signals take less space than analog signals. When we played the telephone game, the digital signal took much less space on the card than the analog signal. Even though this was just a model, it represents how much space each type of signal takes up. If we have a lot of important information to store, it will be easier to fit it all in if the information is digital. Digital signals also sound more like the original, no matter how many times you transmit them. When we looked at the images of the sound, the image of the sound after it was transmitted digitally looked almost identical to the original, but the signal that was transmitted with analog technology looked very different from the original. This shows that when the signals are transmitted, the analog transmission changes the signal. If the information that we want to transmit is important, we should store it digitally so it doesn’t get changed. Since digital signals sound more like the original. even after a long time, and they take less space to store, we should use digital signals to store and send important information.
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Claim, Evidence, Reasoning Scaffolding Ideas Note: Students may be familiar with the term “argument” from writing arguments in their ELA classes. In many science lessons and teaching resources, the “reasoning” section is similar to the argument used in ELA. In the claim-evidence-reasoning (often referred to as CER or Cl-Ev-R) model, the reasoning section is where students construct an explanation for how or why the evidence they cited supports their claim. Differentiating between the evidence and reasoning is difficult for students and takes practice. The evidence consists of the data they collected and/or the observations they made, while the reasoning is an explanation of how or why the data supports the claim. In this case, students will be using evidences collected during class activities and discussions, as well as from readings. Simply listing the data is not enough to support a claim. In the reasoning section, students must describe how the different pieces of evidence can be linked together to support the claim. The first few times students do a CER, they will need some scaffolding. Three different levels of scaffolding are included below, with level III providing the most scaffolding. Level I: Provide students with possible claims and allow them to select the claim they have the most evidence to support. They can then use the evidence they generated to construct their argument. Possible claims: ● We should use digital signals to store and transmit important information ● We should use analog signals to store and transmit important information Additionally, sentence stems could be provided to help students write their reasoning. This could be particularly helpful to ELL students. Level II: Provide students with claims and evidences; allow them to determine which pieces of evidence could support each claim. Sometimes there may be evidences could be used to support multiple claims, or students may have evidence to support more than one claim. After determining which evidences support which claims, students select one claim and use the evidence to construct their argument. You could provide these in a list and allow students to draw lines from the evidence to the claim that it supports, or cut them into strips that students can sort. Possible claims/evidence:
Claims ●
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We should use digital signals to store and transmit important information We should use analog signals to store and transmit important information
Evidences ● ● ● ● ● ● ● ●
The dot signal was transmitted with only one mistake The spoken signal was changed so much that it didn’t contain the same information at the end Sound waves cause air molecules to bump into each other When an analog signal is first recorded, it contains all of the information from the source When a digital signal is first recorded, it contains samples of the information from the source Digital signals take less space than analog signals Background noise cannot interfere with a digital signal while it is being transmitted Background noise can interfere with an analog signal while it is being transmitted
Level III: Provide students with only one claim and a list of evidences (these could be from the examples in the table above). Students determine which of the evidences could be used to support the claim, and then use the evidences they selected to write their reasoning. If additional scaffolding is needed: ● Students could be given the claim and the evidence to support it, and then asked to write their reasoning. In this case, students would be responsible to explain why/how the evidence provided supports the claim given to them. ● Sentence stems could be provided to help students write their reasoning; this may be particularly helpful for ELL students. E. Harward
Name _______________________________________________________ period ________ Analog vs. Digital What are the pros and cons of using each type of signal to store and transmit information? How does the structure of each type of signal contribute to its benefits and drawbacks?
Pros
Cons
Analog
Digital
Question: What type of signal should we use to store and transmit important information? Claim: Evidence
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Reasoning
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