Week 1: Wave Properties & Behavior

Grade 8 Science | Rosche

MS-PS4-1

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Need Support?: Look for green and red "Hint" and "Walkthrough" boxes!

NGSS Standards Covered This Week

MS-PS4-2 (NEW this cycle)

What it means: Develop and use a model to describe that waves are reflected, absorbed, or transmitted through various materials depending on the wave type and material.

In student language: I can explain why WiFi passes through walls but visible light doesn't, using wavelength and material properties.

Spiral Standards from Cycles 3 & 4

  • MS-LS2-3: Energy flow in ecosystems (Cycle 4)
  • MS-LS4-4: Natural selection and adaptation (Cycle 3)

How These Connect (3-Dimensional Learning)

Dimension What You'll Practice
SEP-2 Developing Models Model wave behaviors (reflection, refraction, diffraction, transmission)
SEP-3 Planning Investigations Design experiments to test wave-material interactions
DCI PS4.A/B Wave Properties Understand how wavelength affects material interactions
CCC-1/2/6 Patterns, Cause & Effect, Structure & Function Connect wavelength to predictable interaction patterns

The Phenomenon: The WiFi vs Flashlight Mystery

Learning Targets

By the end of this week, you will be able to:

Success Criteria – How You'll Know You've Got It

Target 1: Explain that waves transfer energy without transferring matter

Self-check: Can I explain why a cork bobs but doesn't travel when a wave passes?

Target 2: Describe how wavelength affects wave-material interactions

Self-check: Can I explain why WiFi passes through walls but light doesn't?

Target 3: Model reflection, refraction, absorption, and transmission

Self-check: Can I identify which wave behavior is happening in different scenarios?

Target 4: Design investigations to test wave behavior with different materials

Self-check: Can I design a barrier that blocks some waves while allowing others?

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Diagram comparing WiFi radio waves (12 cm wavelength) passing through a wall versus visible light (500 nm) being blocked by the same wall
Schematic: wireless router broadcasting concentric radio wavefronts to a laptop, phone, and tablet
A home WiFi router broadcasting ~12 cm radio waves through walls. Visible light is 240,000Γ— shorter β€” that's why it can't do the same. Wikimedia Commons / CC BY-SA

Your home WiFi signal passes through walls, floors, and furniture to reach your devices in any room. But if you try to shine a flashlight through those same walls, no light gets through.

Here's the weird part: BOTH WiFi and visible light are electromagnetic waves!

  • WiFi wavelength: ~12 cm (about the width of your hand)
  • Visible light wavelength: ~500 nm (0.0000005 metersβ€”microscopic!)
  • WiFi waves are 240,000Γ— LONGER than visible light waves!

Focus Question: How can we "see through walls" with WiFi but not with flashlights?

St. Louis Connection & Why This Matters

St. Louis Connection

Boeing St. Louis uses wave technology extensively β€” radar systems, electromagnetic testing, and signal processing all rely on the wave properties and behaviors you are studying this week.

Step-by-Step Problem Solving

Schematic of two coupled pendulums showing energy transferring from pendulum A to pendulum B through a connecting spring over three time snapshots
Animation unavailable.
Watch: Coupled oscillators transfer energy in waves β€” the basis of mechanical wave propagation. | Wikimedia Commons
COMPLETE THE HOOK FORM

Complete the hook form below.

Station 1 – Wave Tank Investigation

20 Points | ~18 Minutes

Your Mission: Discover Wave Behaviors

Comparison diagram of transverse and longitudinal waves showing the difference in particle motion relative to wave direction
Cross-section diagram of an ocean wave with labeled crest, trough, amplitude, and wavelength showing transverse wave anatomy
Ocean waves: a real transverse wave. Water moves up-down; the wave pattern moves sideways. Photo: Roger McLassus / Wikimedia Commons / CC BY-SA 3.0
Diagram showing wave properties: wavelength (crest to crest), amplitude (height), frequency (waves per second), and wave speed
Ripple tank demonstration showing circular wave patterns radiating outward from a point source, illustrating wavelength and wave propagation in water
Coupled oscillations in a physics demonstration β€” the same math that describes all waves. Wikimedia Commons / CC BY-SA

The Four Wave Behaviors

Behavior What Happens Example
REFLECTION Wave bounces off barrier Echo, mirror
REFRACTION Wave bends when changing medium Straw looks bent in water
DIFFRACTION Wave spreads around obstacles Hearing around corners
TRANSMISSION Wave passes through material Light through glass
POE Protocol for Simulations (Predict-Observe-Explain)

PREDICT (Before you start):

What do you think will happen when you change the wavelength? When you add a barrier? Write your predictions in the form BEFORE running the simulation.

OBSERVE (While using simulation):

Run the simulation and record what you SEE in the data table. How do different wavelengths behave? What happens at barriers and gaps?

EXPLAIN (After investigation):

Compare your predictions to observations. What patterns did you find? How does wavelength affect reflection, diffraction, and transmission? Connect to wave physics!

Interactive: PhET Wave Interference Simulation (Click to expand)

How to use: Create waves, add barriers, and observe how waves reflect, refract, and diffract!

Your Simulation Summary
Your prediction: β€”
Trial results: β€”
Average result: β€”
Need extra support? Click here for hints and sentence starters

Key Concept Reminder:

  • Waves transfer ENERGY, not matter
  • Angle in = angle out for reflection
  • Longer wavelengths diffract more around obstacles

Sentence Starters:

  • "Sound waves can bend around corners because..."
  • "The straw looks bent because light waves..."
  • "Energy is conserved when a wave is absorbed because..."

Word Bank:

wavelength β€’ frequency β€’ reflection β€’ refraction β€’ diffraction β€’ transmission β€’ absorption β€’ amplitude β€’ medium β€’ oscillate

πŸ†˜ Stuck? Click here for step-by-step help

Try these steps in order:

  1. Review the 4 wave behaviors table above
  2. For each scenario, ask: "Does the wave bounce, bend, spread, or pass through?"
  3. Watch: Search "Wave Behaviors Explained"
  4. Still stuck? Email Mr. Rosche with your specific question
COMPLETE THE STATION 1 FORM

Identify wave behaviors and explain the energy transfer.

Complete Your Worksheet

Complete the "Station 1" box in the "STATION 1 & 2 NOTES" section:

  • Wave behaviors observed: reflection, refraction, diffraction
  • How wavelength affects behavior: (your observations)
  • Key insight: (one sentence summary)

Station 2 – Electromagnetic Spectrum Exploration

20 Points | ~15 Minutes

Your Mission: Explore the EM Spectrum

Diagram of the electromagnetic spectrum from radio waves through microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays with wavelength and frequency scales
Glass prism splitting white light into a rainbow of colors, showing that visible light contains all wavelengths from 380 nm (violet) to 700 nm (red)
A prism splits white light into the visible spectrum β€” the tiny slice of the EM spectrum human eyes can detect. Wikimedia Commons / CC BY-SA
Diagram showing reflection, absorption, and transmission of waves at material boundaries β€” what happens when waves encounter different materials
X-ray radiograph of a human hand showing transmission through soft tissue (dark) and absorption by bone (light white areas), demonstrating how different EM wavelengths interact with different materials
X-rays (short EM waves) transmit through soft tissue but are absorbed by dense bone β€” a real-world example of wave-material interaction. Wikimedia Commons / public domain

The Electromagnetic Spectrum

Wave Type Wavelength Energy Common Use
Radio 1 km - 1 m LOW AM/FM, WiFi
Microwave 1 m - 1 mm ↓ Cell phones, cooking
Infrared 1 mm - 700 nm ↓ Remote controls, heat
VISIBLE 700 - 400 nm ↓ Human eyes can see!
Ultraviolet 400 - 10 nm ↓ Sunburn, sterilization
X-ray 10 - 0.01 nm ↓ Medical imaging
Gamma < 0.01 nm HIGH Cancer treatment

KEY: Longer wavelength = Lower energy = More likely to pass through materials

WORKED EXAMPLE: Analyzing Wavelength-Material Interactions

Learn by following an expert's thinking process. Week 1 shows ALL steps.

PROBLEM:

A concrete wall (20 cm thick) blocks your cell phone signal (microwave, Ξ» = 12 cm) but radio waves (Ξ» = 3 m) from an AM station pass through easily. Why?

STEP 1: Identify wavelengths and compare to material

Expert thinks: "First, I need to organize what I know about the waves:"

  • Cell phone microwave: Ξ» = 12 cm = 0.12 m
  • AM radio wave: Ξ» = 3 m
  • Wall thickness: 20 cm = 0.2 m
  • "The radio wave is 25Γ— LONGER than the microwave!"

STEP 2: Apply wave-material interaction principles

Expert thinks: "Concrete is a composite with small gaps and pores (typically 1-5 cm)."

  • Microwave (12 cm) is LARGER than most gaps β†’ gets absorbed/reflected
  • Radio wave (3 m = 300 cm) is MUCH LARGER than gaps β†’ diffracts around obstacles within the material
  • "Long waves bend around small obstacles; short waves get blocked!"

STEP 3: Consider energy absorption

Expert thinks: "Concrete contains water molecules and metal reinforcement."

  • Microwaves (higher frequency) excite water molecules β†’ energy absorbed as heat
  • Radio waves (lower frequency) have less energy per photon β†’ less absorption
  • "The microwave's energy matches concrete's absorption bands!"

STEP 4: Construct complete explanation

Expert writes:

"Radio waves pass through concrete while microwaves are blocked because: (1) Radio wavelength (3 m) is much longer than concrete's internal structure, allowing diffraction around obstacles, while microwave wavelength (12 cm) matches the size of gaps and gets blocked; (2) Microwaves have higher frequency and thus more energy to excite water molecules in concrete, causing absorption, while radio waves have insufficient energy for significant absorption."

SELF-EXPLANATION PROMPT:

Why can you hear your neighbor's bass music through a wall more easily than their high-pitched vocals? Use wavelength principles from this worked example to explain. (Hint: Bass = longer wavelength sound waves, vocals = shorter wavelength sound waves.)

Why WiFi Goes Through Walls But Light Doesn't:

  • WiFi wavelength: ~12 cm (120,000,000 nm)
  • Light wavelength: ~500 nm
  • WiFi is 240,000Γ— LONGER
  • Longer waves diffract through gaps in wall materials that block shorter waves!

Engineering Waves in St. Louis: Gateway Arch Integrity Testing

The Gateway Arch uses X-ray testing to check structural steel integrityβ€”exactly the wavelength/transmission properties you're studying. Dr. Katharine M. Flores, a materials scientist at Washington University in St. Louis, studies how different wavelengths penetrate different materials. Engineers use gamma rays for thick steel (short wavelength = high penetration), X-rays for thinner sections, and infrared for surface temperature monitoring. The Arch's stainless steel skin requires constant monitoring because thermal expansion (summer heat vs winter cold) creates stress points. Diverse engineering teamsβ€”including structural engineers ($75k-$120k), materials scientists ($80k-$110k), and NDT (non-destructive testing) technicians ($45k-$75k)β€”use wave physics to protect the millions of visitors each year. Your understanding of how wavelength affects material interaction is foundational to infrastructure safety.

Need extra support? Click here for spectrum hints

Memory Trick:

"Randy Moves Into Very Unusual X-treme Games" = Radio, Microwave, Infrared, Visible, UV, X-ray, Gamma (longest to shortest wavelength)

Sentence Starters:

  • "X-rays pass through skin but not bone because..."
  • "Radio waves have lower energy than gamma rays because..."
  • "WiFi passes through walls because its wavelength is..."
COMPLETE THE STATION 2 FORM

Explore the EM spectrum and explain wavelength-material interactions.

Station 2 Form β€” Form pending deployment

This form is authored but has not yet been published to Google Forms. Your teacher will share the link once it is live. No action needed from students until then.

Complete Your Worksheet

Complete the "Station 2" box in the "STATION 1 & 2 NOTES" section:

  • EM spectrum pattern: longer wavelength = lower energy = more likely to pass through
  • Why WiFi passes through walls but light does not
  • Key insight: (one sentence summary)

COMPLETE THE STATION 2 FORM

Complete the form below for Station 2.

Complete Your Worksheet

Complete the "Station 3 β€” Engineering Design" section:

  • Materials tested and wave behaviors: (reflect/absorb/transmit)
  • Design choice and justification
  • Key insight: (one sentence summary)

COMPLETE THE STATION 2 FORM

Complete the form below for Station 2.

Complete Your Worksheet

Complete the "DAY 2 EXIT TICKET" and "SCIENCE CIRCLE" sections:

  • Check your answers match your reasoning from the stations
  • Add any wave evidence you found at the stations

COMPLETE THE STATION 2 FORM

Complete the form below for Station 2.

Week 1 Summary: What You Learned

Energy Transfer: Waves transfer ENERGY, not matterβ€”a cork bobs but doesn't travel

Wave Behaviors: Reflection, refraction, diffraction, and transmission

EM Spectrum: Longer wavelength = lower energy = more likely to pass through materials

WiFi vs Light: WiFi has 240,000Γ— longer wavelength, so it diffracts through wall gaps

Week 1 Complete!

Next Week: How do waves carry and transmit information?