Unit 2 · Light, Sound & Information · Week 5 · Unit Capstone

Can you design a way to send a clear message across a distance — and explain the waves doing the work?

Two friends need to signal each other across a noisy canyon. Can you design a communication method — using what you know about waves — that gets the message through reliably? And can you explain, using wave properties and information encoding, why your design works?

SEP: Constructing Explanations & Designing Solutions · Obtaining, Evaluating & Communicating Information DCI: PS4.A Wave Properties · PS4.B Electromagnetic Radiation · PS4.C Information Technologies & Instrumentation CCC: Patterns · Structure & Function

NGSS MS-PS4-3 · MS-PS4-1 · MS-PS4-2 ~60 minutes (performance task) Learner code: —

Make this lesson work for you:

Start here

How we work today (our expectations)

This is YOUR thinking — bring in everything you built this unit
There is more than one good design — explain why yours works
Evidence and reasoning matter more than a "correct answer"
Open any support panel — they belong to you, any time

30-second check-in self-awareness + self-management

Unit 2 ends today. Before anything else, think back to Week 1 — you were wondering how a phone gets a message across the world in seconds. You have four weeks of ideas about that now. Take one slow breath. Name one idea from this unit that feels solid. That's your anchor for the next 60 minutes.

Do-Now Retrieve the whole unit

Four questions — one from each week. No looking back. Pulling ideas from memory now makes the design task easier later.

Week 1 spiral A wave carries energy from one place to another. Name two wave properties you could change to change how much energy a wave carries. (Hint: think about what you can see change in an ocean wave.)
Week 2 spiral When a wave hits a new material, three things can happen. Name all three — and give one everyday example of each (for either sound or light).
Week 3 spiral Why can you hear someone in the next room through a closed door, but not see them? What does that tell you about how sound and light travel differently?
Week 4 spiral A digital signal stores information as a pattern of 1s and 0s. An analog signal stores it as a smoothly varying wave. Why does a digital signal usually arrive at the other end with less noise than an analog signal?

The anchor phenomenon

Person A needs to send an exact message to Person B across a wide, noisy canyon. One wave type crosses cleanly; the other gets scrambled by noise. Your job is to design the solution — and explain the wave science behind it.

Imagine two friends who work as park rangers on opposite sides of a canyon that is 600 metres wide and filled with wind noise. They need to send each other a short coded message every hour — something as simple as "all clear" or "emergency." They tried shouting. The wind and echo made it impossible to understand. They tried a walkie-talkie with an analog signal — the canyon walls reflected and scattered the signal so badly it sounded like static. One of them just got a new device that uses a digitized light signal instead, and the message got through perfectly on the first try. Why did the digitized light signal succeed where the analog sound signal failed? And could they design an even simpler, lower-tech version that still works?

Notice & Wonder. Write one thing you notice from the diagram that connects to a week earlier in this unit. Then write the one question you most want answered by the end of today.

Tie it together One unit, one connected model

Weeks 1–4 each gave you one piece. Here they connect into a single engineering insight.

Look at the unit arc: Week 1 — waves carry energy; amplitude and frequency control how much energy they carry and what you sense. Week 2 — when a wave hits a new material it can reflect, absorb, or transmit; which one happens depends on the material's properties. Week 3 — sound needs a medium to travel (it cannot cross a vacuum); light does not — it can travel through empty space and through transparent materials. Week 4 — information encoded digitally (as a pattern of on/off — 1s and 0s) is far more reliable than information encoded in a continuously varying analog wave, because even a noisy or distorted digital signal can be reconstructed accurately. The unifying engineering idea sitting beneath all four: we choose the right wave type and the right encoding method to carry information reliably across the specific obstacle in front of us. A designer who understands wave behavior — reflection, absorption, transmission, and the medium requirement — plus digital encoding can engineer a communication system for almost any scenario.

Worked example — applying the unit model to the canyon scenario (read before you design)

Why sound failed: Sound waves need a medium. The canyon has air — so sound can travel. But canyon walls reflect and scatter sound waves at many angles (echoes), the wind carries its own pressure waves (noise), and the reflected waves arrive at the receiver out-of-phase, distorting the pattern. An analog sound signal — where the information is in the exact shape of the wave — cannot survive that scrambling intact.

Why a digitized light signal succeeded: Light does not need a medium, so it travels across the open canyon without scattering in air the same way. A direct line-of-sight light beam (such as a laser or bright LED) can be aimed so it hits the receiver without reflecting off canyon walls. Most critically, the signal is digital: the message is encoded as a series of short flashes (on = 1, off = 0). Even if some flashes are slightly dimmer from absorption by dust in the air, the receiver still reads bright vs. dark — "yes" vs. "no" — and reconstructs the exact message. Digital encoding makes the signal resistant to noise.

The design principle: choose a wave type that can cross the obstacle (light for an open gap, not blocked by the canyon walls); encode the information digitally so noise cannot destroy the pattern; keep the path as direct as possible to minimize reflections and absorption.

Show me a connection table linking all four weeks to the design problem Tier 2 · organizer

Fill in or use this table to trace each week's idea to the canyon scenario:

Week 1 (waves carry energy): The light signal carries energy from A to B. Higher amplitude = ________ at the receiver.

Week 2 (reflect / absorb / transmit): The canyon walls ________ sound (scatter it in many directions). The light beam ________ through the air to the receiver.

Week 3 (medium requirement): Sound needs a medium. Light ________ need a medium. So across an open gap with line of sight, ________ is the better wave type.

Week 4 (digital vs. analog): A digital light signal encodes the message as ________ (on/off). Even with some noise, the receiver can still tell ________ apart and reconstruct the exact message.

Performance task Design your wave-based communication system

This is the unit summative task. Use everything from Weeks 1–4. Complete all three parts. All response modes are equally valid — write, draw a labeled diagram, or record yourself explaining it step-by-step.

✍️ Write your design + explanation 🎨 Draw a labeled diagram + annotate 🗣️ Record yourself explaining it step-by-step

Step 1 — Choose your scenario and your wave type.

Choose a scenario and circle or write your choice:

Scenario: ☐ Two friends signaling across a noisy canyon (open air, 600 m) ☐ Two classrooms in the same building, separated by a wall ☐ My own scenario: _______________

Wave type I will use: ☐ Light (visible or infrared) ☐ Sound ☐ Both — a combination

I chose this wave type because: _______________________________________________

Think about: Does the wave need a medium? What obstacles will it face — reflection, absorption, noise? Can my wave cross this specific gap without being blocked or scrambled?

Step 2 — Describe your encoding method and explain why it keeps the message reliable.

A message only matters if it arrives correctly. In 3–5 sentences (or a labeled diagram), answer:

How will you encode the message — analog (a continuously varying signal) or digital (a pattern of on/off signals)? Describe the specific pattern you would use. For example: "three short flashes = all clear; one long flash = emergency."
How does your encoding method protect the message from the noise in your scenario? Use the words digital or analog and connect to what you learned in Week 4.
What is one way the signal might still be degraded or lost in your scenario — and what design choice could reduce that problem?

Step 3 — Explain the wave behavior on the path from sender to receiver.

Your wave will encounter at least one material boundary on its journey. Show that you understand wave behavior by doing one of the following for your scenario:

Draw the wave's path and label where reflection, absorption, or transmission happens — and explain whether each one helps or hurts your design.
Write a two-paragraph explanation: paragraph 1 describes what happens to your wave at the first obstacle it hits (using at least two of: reflect, absorb, transmit, medium, amplitude); paragraph 2 explains what the receiver needs to do to interpret the signal correctly.
Create a comparison table: your chosen wave type vs. the other wave type — for each, evaluate whether it reflects/absorbs/transmits through your specific obstacle, whether it needs a medium, and whether digital encoding helps or doesn't change things.

Step 4 — Describe how you would test and improve your design.

How would you test whether your system successfully sent the correct message? (What would you measure or observe? What counts as success?)
Describe one change to your design you would try if the first test failed — and explain, using wave science, why that change should help.

I want sentence frames and a design template Tier 2 · frames + template

Step 1 sentence frames:

I chose light / sound (circle one) because ________. In my scenario, this wave needs / does not need a medium to travel. The main obstacle is ________, and my wave type handles it by ________.

Step 2 sentence frames:

My encoding method is digital / analog (circle one). The specific pattern I will use is ________. This protects the message from noise because ________. One way the signal could still be degraded is ________. I could reduce this by ________.

Step 3 sentence frames:

When my wave hits [the obstacle], it is mostly reflected / absorbed / transmitted (circle one). This helps / hurts my design because ________. The receiver interprets the signal by ________.

Step 4 sentence frames:

I would test my system by ________. I would know it worked if ________. If the first test failed, I would try ________ because, based on wave behavior, this change would ________.

Word bank: wave · light · sound · medium · amplitude · frequency · reflect · absorb · transmit · digital · analog · signal · noise · encode · decode · pattern · reliable · line of sight · interference · receiver · sender · obstacle · 1 · 0 · on · off

Let's make it concrete first — guided choices + analogies Tier 3 · re-teach

Analogy for digital vs. analog (Week 4): Imagine you want to tell your friend "yes" or "no" across a noisy room. If you speak the word (analog — a continuously varying sound), the noise might change "yes" to sound like "guess." But if you hold up a thumbs-up or thumbs-down (digital — two distinct states), even across a crowded, noisy room your friend can still read it correctly. Digital signals work the same way: even a noisy, distorted digital signal is still readable as long as you can tell "on" from "off."

Analogy for wave type choice (Week 3): Sound is like a slinky — it needs something to push through (a medium). Light is like throwing a ball through the air — it can cross open space on its own. If your obstacle is an open gap (like a canyon or an open room), light can cross without needing anything to push through. If the obstacle is a wall, you need to think about whether your wave can transmit through the material or whether you need a different path.

Guided choices for each step:

Step 1: For the canyon scenario, the better wave type is light / sound because ________ does not need a medium and can cross an open gap with a clear line of sight.

Step 2: I will use a digital / analog encoding method. My pattern: 3 short flashes = all clear / 1 long flash = emergency. This works in noise because the receiver only needs to tell on from off / flash from no-flash.

Step 3: When the light beam crosses the canyon, the air mostly transmits / reflects / absorbs it. The receiver interprets the signal by counting the flashes / measuring the brightness.

Step 4: I would test it by sending the "all clear" pattern and confirming the receiver reads it correctly / sending 5 messages and counting how many arrived correctly. If it failed, I would try a brighter light source / a focused beam / moving to higher ground for a clearer line of sight.

Say each answer out loud before writing — one or two sentences per step is enough.

Push my thinking — open engineering with constraints and trade-offs Extension

Engineering constraints to add: Your system must (1) send at least 10 distinct messages (not just "all clear" and "emergency"); (2) work in full daylight, when ambient light is high; (3) use only equipment two hikers could carry; (4) work even when the sender and receiver cannot see each other directly (no line-of-sight).

Trade-off analysis: For each design choice below, describe one advantage and one disadvantage, and identify the wave or information science that explains each:

Using a higher-frequency light source (such as ultraviolet) instead of visible light.
Encoding the message with sound waves bounced off the canyon walls (reflected) instead of direct line-of-sight light.
Using a reflective mirror to redirect the light signal around an obstruction.

Fair test: Design one controlled experiment to compare two versions of your encoding method — e.g., a 2-symbol digital code vs. a 4-symbol digital code. Name your independent variable (what you change), dependent variable (what you measure), and at least two controlled variables (what you keep the same).

Go deeper: Modern undersea internet cables carry data as digitized light pulses (fiber optics) through glass fibers thousands of kilometres long. Using everything from this unit, explain: (a) why light rather than sound is used; (b) why digital rather than analog encoding is used; (c) what happens to the signal's amplitude over a very long distance, and what engineers do to compensate.

How your work will be evaluated — the 3D rubric

Read this before you write. The strongest response uses all three dimensions together — science practices, the core wave ideas, and the crosscutting concept.

Performance Task Rubric — Unit 2 Capstone (MS-PS4-3, MS-PS4-1, MS-PS4-2)

Dimension	Emerging — getting started	Developing — on the way	Proficient — you've got it	Advanced — you're going beyond
SEP: Constructing Explanations & Designing Solutions · Obtaining, Evaluating & Communicating Information	Names a wave type or a device but does not explain the reasoning; description is incomplete or lists features without connecting to a goal or scenario.	Identifies the wave type with a basic reason for choosing it; describes an encoding method and at least one test, though the connection between design choices and the specific obstacle is partial.	Clearly justifies the wave-type choice using the obstacle in the scenario; describes a specific digital or analog encoding scheme; proposes a testable design with at least one improvement; explanation connects wave science to each design choice.	Articulates multiple design criteria and constraints; conducts a logical trade-off analysis between wave types or encoding methods; proposes a fair test with independent, dependent, and controlled variables named; communicates the reasoning in a form a reader could act on.
DCI: PS4.A Wave Properties · PS4.B Electromagnetic Radiation · PS4.C Information Technologies	Mentions that waves carry information but does not connect wave properties (reflection, absorption, transmission, medium requirement) to the scenario; may have a misconception (e.g., "light can't cross a gap").	Connects at least one wave behavior (e.g., reflection or medium requirement) to the design choice; mentions digital encoding but does not fully explain why it resists noise; some wave vocabulary is correct.	Correctly explains why the chosen wave type can cross the specific obstacle, using at least two wave behaviors (e.g., transmission through air + no medium needed for light); explains that digital encoding makes the signal more reliable because the receiver only needs to distinguish on from off; uses wave vocabulary accurately.	Integrates wave property details with encoding details: e.g., explains how amplitude reduction over distance affects readability and how digital encoding compensates; distinguishes between noise added to the wave and noise added to the encoding; connects to a real technology (fiber optics, Morse code, AM/FM radio) with accurate wave science.
CCC: Patterns · Structure & Function	Notes that the design has parts but does not connect the structure of the encoding (pattern) to its function (reliable reception); no reference to the pattern of digital signals or the function of each design choice.	Identifies that a digital signal has a pattern (on/off) and that this pattern carries information; or describes the structure of the device without fully explaining how that structure produces reliable function across the obstacle.	Explains that the repeated, predictable pattern of digital encoding (on/off = 1/0) is the structural feature that makes it resistant to noise (function); connects the physical structure of the path (line-of-sight, material boundaries) to the function (successful message delivery); describes at least one pattern in wave behavior on the path (e.g., reflection at walls).	Analyzes multiple levels of pattern and function: the pattern at the encoding level (digital bits), the pattern at the wave level (amplitude, frequency), and the pattern at the path level (where reflection and transmission occur); explains how the structure of the whole system — sender, medium, receiver, encoding — produces the function of reliable communication; generalizes to other systems (e.g., Morse code, braille, binary).

Check yourself Unit synthesis — did it connect?

Success criteria — I can:

choose a wave type for a communication scenario and justify the choice using wave properties (medium requirement, reflection, absorption, transmission);
describe a digital encoding method and explain why it is more reliable than an analog signal in a noisy environment;
trace the path of a wave from sender to receiver and identify where wave behaviors (reflect, absorb, transmit) help or hurt the design;
connect all four unit weeks into one engineering insight: choosing the right wave and encoding for the obstacle makes reliable communication possible.

Your message got through the noisy canyon clearly. Your friend received exactly the right pattern of flashes. Which design choice mattered most — and why?

Re-teach: why digital encoding beats analog encoding in a noisy channel Tier 3

The core idea from Week 4: An analog signal carries information in the exact shape of the wave — its precise amplitude and frequency at every moment. Any distortion (noise, reflection, absorption) changes that shape, and the message is lost or garbled.

A digital signal carries information differently: it only uses two states — on (1) or off (0). The receiver doesn't need to measure the exact amplitude or shape. It just asks: "Is there a signal or not right now?" Even if the signal is weakened or slightly distorted, a dimmer flash is still a flash; a gap is still a gap. The pattern — the sequence of 1s and 0s — survives the noise.

Think of it this way: Suppose you are reading a message written in huge block letters versus a message written in tiny, precise cursive. If someone smudges the paper, the huge block letters are still readable. The tiny cursive becomes illegible. Digital encoding is the "huge block letters" of signal design.

Now re-read option B. It describes this principle correctly. Try explaining it in your own words before moving on.

Reflect, then show what you know

Metacognitive reflection metacognition + SEL

Answer at least one:

What is one idea from this unit that you understand now that didn't make sense to you in Week 1? What clicked for you — and when?
Which of the four weeks was the hardest for you, and what do you think made it hard?
If you had to explain "why digital signals are more reliable than analog signals" to a younger student using only a hand gesture analogy, what would you say?

Self-assessment against the rubric responsible decision-making

Look back at the 3D rubric. For each row (SEP, DCI, CCC), write the level that best describes your performance task response — Emerging, Developing, Proficient, or Advanced. Then write one thing you would add or change to move up one level.

SEP: I am at _______________. One thing I would add: _______________.

DCI: I am at _______________. One thing I would add: _______________.

CCC: I am at _______________. One thing I would add: _______________.

Exit ticket — answer on paper or in your notebook. (2 new · 2 spiral · 1 transfer)

New In one or two sentences, explain why a digital signal is more reliable than an analog signal when the transmission path is noisy. Use the words pattern, on, off, and noise.
New You want to send a message through a concrete wall between two classrooms. Which would work better — a light signal or a sound signal? Explain your answer using what you know about how each wave interacts with dense materials (transmit, reflect, absorb).
Spiral — Week 2 A canyon wall reflects a sound wave that was supposed to reach the receiver directly. Explain how the reflected copy of the signal interferes with the original — and why this is more damaging for an analog signal than a digital one.
Spiral — Week 1 If you increase the amplitude of a light signal you are using to communicate across the canyon, does that make it more reliable? Explain your answer using wave energy and what you know about digital vs. analog encoding.
Transfer A biologist wants to track the movements of whales in deep ocean water, where light does not penetrate. She attaches a tag to a whale that sends a signal back to a receiver on a boat. Using everything from this unit, recommend: (a) whether she should use light or sound, and explain why; (b) whether the signal should be digital or analog, and explain why; (c) describe one challenge with her chosen wave type in the ocean environment and how the design might address it.

Educator panel — facilitation, accommodations, rubric guidance, answer key, research rationale

At a glance

Primary standard: NGSS MS-PS4-3 — Integrate qualitative scientific and technical information to support the claim that digitized signals are a more reliable way to encode and transmit information than analog signals. Integrated standards: MS-PS4-1 (use mathematical representations of waves to describe patterns in amplitude, wavelength, and frequency); MS-PS4-2 (develop and use a model to describe how light reflects, absorbs, and transmits). 3D lens: SEP Constructing Explanations & Designing Solutions + Obtaining, Evaluating & Communicating Information · DCI PS4.A Wave Properties + PS4.B Electromagnetic Radiation + PS4.C Information Technologies & Instrumentation · CCC Patterns + Structure & Function.

Materials needed: None required beyond paper and pencil. Optional enhancements: a bright LED flashlight (to demo a direct light beam), a laser pointer (to demo line-of-sight), a phone with a flashlight app set to blink (to demo digital encoding). None of these are required; the lesson works fully with the SVG and the written scenario.

Estimated time: 60 minutes. The performance task (Steps 1–4) takes 20–25 minutes for most learners. Budget extra time for the rubric self-assessment. The exit ticket can be assigned for homework if the period runs short.

Facilitation arc (Rosenshine + engineering design loop)

Do-Now retrieval (5 min) — students work individually; do not provide answers yet. Use a quick think-pair-share to activate the four weeks of prior knowledge before the anchor phenomenon.
Phenomenon + notice/wonder (5 min) — display the SVG; cold-call two students to share a notice and a wonder. Write wonders on the board. Ask: "What from earlier this unit does this remind you of?"
Synthesis build + worked example (8 min) — read the "Tie it together" passage as a class. Walk through the worked example. Ask: "Which week explains why the sound signal failed? Which explains why the digital light signal succeeded?" This bridges prior learning to the performance task.
Introduce the performance task + rubric (4 min) — read the rubric aloud together before students begin. Ask: "What would a Proficient response look like for the DCI row?" This is formative previewing (Black & Wiliam, 1998).
Performance task (20–25 min) — students work independently or in pairs. Circulate and prompt: "Can you point to a specific wave behavior from Weeks 1–4 that explains your design choice?" Do not evaluate during this time — ask questions that push reasoning, not questions that give answers.
Self-check + re-teach (4 min) — take a quick poll on the branching self-check (A/B/C/D). Route any A/C/D responders to the re-teach details. Briefly explain the correct reasoning to the whole class before moving to reflection.
Brain break + reflection + exit ticket (10 min) — reflection is structured; exit is written individually (or assigned as homework).

IEP / 504 accommodation cards

Common accommodations mapped to this lesson

Accommodation	How it's already built in / what to do
Text read aloud	Every passage has a Listen button (TTS via Web Speech API); the simplified toggle shortens all passages.
Reduced reading load	"Reading: Simplified" swaps in plain-language text throughout.
Chunking / extended time	Performance task is broken into four clearly numbered steps; progress saves automatically to localStorage.
Sentence frames / word bank	Tier-2 support panel provides frames for all four steps and a word bank of 28 terms.
Concrete analogy / reduced load	Tier-3 panel provides the "thumbs-up / thumbs-down vs. spoken word" analogy for digital encoding and the "slinky vs. ball throw" analogy for medium requirement; guided-choice versions of each step are provided.
Alternative response mode	Students may write, draw a labeled diagram, or record a verbal explanation — all three are explicitly accepted as equally valid.
Behavior / focus (504, ADHD)	Named expectations (PBIS), 30-second check-in, built-in brain break with movement, four short numbered steps.
Multilingual / EL	Simplified text toggle, visual SVG anchor showing wave paths and labels, word bank in Tier-2, home-language reflection allowed (metacognitive prompt).
IEP goal: written expression	Accept diagram + minimal annotation as a complete response to Steps 2–3; verbal recording or oral explanation to the teacher is also valid.
IEP goal: science reasoning	Rubric's Emerging and Developing descriptors define the scaffolded floor — any response that identifies a wave type and mentions encoding is gaining in the right direction. The Tier-3 guided-choice panel sets a concrete floor for success.

Rubric scoring guidance + exemplar response sketch

What a Proficient response looks like (canyon / light / digital):

SEP: "I am designing a light-signal system for the canyon. I chose light because it does not need a medium and can travel across an open gap in a straight line. I will encode the message as three short flashes for 'all clear' and one long flash for 'emergency.' I would test it by having a partner on the other side read back the message I sent. If it failed, I would try aiming more carefully or using a brighter source."
DCI: "Light waves can cross the canyon because they don't need a medium — they travel through air easily and the air mostly transmits rather than absorbs visible light. Sound waves get reflected and scattered by the canyon walls and scrambled by wind, making the analog sound signal unreadable. My digital light signal works because the receiver only has to tell 'flash' from 'no flash' — two clearly different states. Even if the beam loses some amplitude crossing the canyon, the on/off pattern is still readable."
CCC: "The structure of my encoding — a pattern of short and long flashes — is what makes reliable reception possible. Each flash is a distinct, readable symbol. Even when noise changes the amplitude slightly, the pattern (3 short = all clear, 1 long = emergency) can still be recognized. This is structure (binary pattern) producing function (accurate message delivery)."

Common errors to address:

"More amplitude always means a more reliable signal" — redirect to the digital encoding concept: amplitude determines reach, but encoding determines whether the pattern survives noise. A very loud/bright analog signal is still analog.
"Sound can't cross the canyon at all" — sound does travel through air; the issue is that it gets reflected and scattered into an unreadable analog mess. The problem is noise + analog encoding, not that sound literally can't cross open air.
Confusing "digital" with "electronic" — digital just means two-state (on/off, 1/0). Morse code, semaphore flags, and blinking a flashlight can all be digital; digital doesn't require electricity.
Not connecting CCC Patterns to the encoding — prompt: "What's the structure of your on/off pattern? How does that structure produce the function of noise resistance?"

Exit ticket answer key

A digital signal carries information as a pattern of on and off states. Even when noise is present and changes the signal's strength, the receiver only needs to detect "on" (signal present) vs. "off" (no signal) — two clearly different states. As long as noise can't turn an "on" completely off or vice versa, the pattern survives and the message arrives correctly.
Sound would work better through a concrete wall. Concrete is a dense solid, and sound waves (mechanical vibrations) can travel through solids — the wall vibrates and passes sound to the other side (transmission through the medium). Visible light waves are mostly absorbed or reflected by concrete and cannot transmit through it. (Note: students may reason that neither works well, which is acceptable if they correctly explain why — the key is connecting material properties to wave behavior.)
The reflected copy arrives at the receiver slightly later and from a slightly different angle than the direct signal, so the two copies interfere — they can add together (louder at some moments) or cancel out (quieter at others), distorting the wave's shape. For an analog signal, this shape distortion garbles the information because the information is encoded in the exact shape of the wave. For a digital signal, even a distorted "on" state is still recognizable as "on" as long as the receiver can distinguish it from "off" — the pattern of 1s and 0s survives the distortion better.
Increasing amplitude makes the signal travel farther before it fades below a readable level — so it helps with distance. However, amplitude alone doesn't make the signal more reliable against noise. If the signal is digital (on/off pattern), increasing amplitude gives the receiver more margin to distinguish "on" from "off" despite noise — so it indirectly helps. But if the signal is still analog, more amplitude does not fix the noise problem; the noise just distorts a louder version of the same wave. The reliability comes from the encoding method, not just the amplitude.
(a) Sound — in the deep ocean, light does not penetrate more than a few hundred metres because water absorbs it strongly. Sound waves travel extremely well through water (water is a dense medium that transmits sound efficiently at very long distances — this is how sonar and whale communication work). (b) Digital — the ocean is full of biological and mechanical noise; a digital signal encoded as pulses (on/off) can be detected reliably even when the signal is weakened by distance and distorted by background noise, whereas an analog signal's exact wave shape would be scrambled. (c) One challenge: at very long distances, the sound signal loses amplitude and may be absorbed by the ocean or scattered by temperature layers (thermoclines). Engineers address this by using signal amplifiers (repeaters) along the path and by choosing frequencies that are absorbed less by seawater.

Why it's designed this way — research rationale

Why a performance task, not a recall test? The NGSS and A Framework for K-12 Science Education (NRC, 2012) explicitly call for assessments that require students to use science practices, core ideas, and crosscutting concepts together — not recite them in isolation. A student who can recite "digital signals are more reliable" without being able to apply it to a new engineering scenario has not reached MS-PS4-3, which specifically asks students to "integrate qualitative scientific and technical information to support the claim." The canyon communication design task requires transfer to a new scenario: students must choose a wave type, justify it using wave behavior from MS-PS4-1 and MS-PS4-2, design an encoding method grounded in MS-PS4-3, and propose a test — all simultaneously, in a scenario they have not seen before.

Strengths-first rubric design (Black & Wiliam, 1998; Wiliam, 2011): The rubric labels progress from Emerging through Advanced — not Failing, Insufficient, etc. The descriptors name what to do next at each level. Students who read the rubric before writing use it as a pre-task success checklist, which is among the highest-impact formative practices (Wiliam, 2011, p. 127). The "Advanced" column gives every student a visible target beyond Proficient without requiring anyone to reach it.

Three-dimensional rubric rows: Each row names one NGSS dimension so the teacher can diagnose which dimension needs re-teaching. A student at Emerging on DCI but Proficient on SEP needs entirely different feedback than the reverse. Flat scoring (a single total score) obscures this diagnostic signal.

Interleaved retrieval in the Do-Now (Roediger & Karpicke, 2006; Rohrer, 2012): One item per prior week. The spacing and interleaving effect is well-established: testing memory for earlier content activates the schema needed for current learning and strengthens long-term retention more than re-reading. The Do-Now items are calibrated so each one maps to a wave concept the performance task will ask students to apply.

UDL + MTSS (CAST UDL Guidelines 3.0, 2024; Fuchs & Fuchs, 2017): Tier-2 sentence frames and a word bank lower the language load without reducing the cognitive goal. Tier-3 guided-choice options and concrete analogies (thumbs-up/down for digital encoding; slinky vs. ball throw for medium requirement) scaffold the conceptual floor while targeting the same three-dimensional standard. The Extension adds engineering constraints and a fair-test design for students ready for above-grade challenge. None of the tiers reduces the goal — all three target MS-PS4-3 at Proficient or above.

Phenomenon-first design (Reiser et al., 2021; NRC, 2012): The canyon scenario was chosen because it is (a) accessible — no specialized knowledge required to imagine it; (b) genuinely three-dimensional — it cannot be solved without integrating wave properties, medium considerations, and encoding reasoning; and (c) connected to the unit's anchor from Week 1 (how does a message cross distance at all?), completing the unit storyline.