LyfeLabz | Wave Behavior

6.MS-PS4-2 Develop and use a model to describe that waves are reflected, absorbed, or transmitted through various materials.

6.MS-PS4-1 Use diagrams and other representations to show that both light and sound are waves that move and transfer energy.

Mystery

Three Objects. One Question.

You're outside a classroom. A door, a window, and a brick wall are between you and what's happening inside. Each surface interacts with sound and light differently.

🚪

The Wooden Door

You can hear voices inside, but you cannot see through the door.

Sound gets through. Light doesn't. Why?

Click to look closer

🪟

The Window

You can see inside clearly, and the room sounds a little louder near the glass.

Light passes through easily. Why?

Click to look closer

🧱

The Brick Wall

You cannot see through it, and you barely hear anything.

Most of the energy seems to just... stop. Where does it go?

Click to look closer

💡 Same energy. The same sound waves and light waves from inside the classroom are hitting all three surfaces.

🤔 Why do the same waves behave so differently when they hit different materials?

The question: What determines what happens when a wave reaches matter? The wave didn't make a choice. The surface didn't choose. Something about the physics of each material is causing this, and this whole lesson is about figuring out what.

What We Already Know

Waves Carry Energy: And Energy Has to Go Somewhere

Before we solve the mystery, there's one rule we need to remember.

Mechanical Waves

Need a medium to travel

Sound, water, and seismic waves all travel by pushing matter from particle to particle.

No medium → no mechanical wave. That's why you can't hear an explosion in space.

Electromagnetic Waves

Need no medium at all

Light, radio waves, and X-rays travel as disturbances in electric and magnetic fields, not in matter.

Empty space is fine. That's how sunlight crosses 93 million miles of vacuum to reach Earth.

Waves carry energy.

Energy cannot be created or destroyed.

So when a wave reaches a surface, the energy must go somewhere.

In this lesson, you'll discover the three places that energy can go.

When Waves Bounce

The Wave That Came Back

Stand in a canyon and shout. A few seconds later, you hear your own voice return. How did the sound come back?

🏔️ You shout in a canyon. Your voice comes back a moment later: the exact sound, delayed.

🪞 You stand in front of a mirror. Light bounces back and reaches your eyes; your reflection appears.

🤔

Think about it: What do you think is happening to the wave's energy at the moment it hits the surface? Make a prediction.

Now we have a word for it

Reflection happens when a wave bounces off a surface instead of passing through it.

🏔️

Echo in a canyon or caveSound

🪞

Your reflection in a mirrorLight

🦇

Bat echolocation: sound bounces off preySound

🛥️

Sonar: bounces off the ocean floorSound

🎵

Concert halls shaped to reflect sound toward the audienceSound

☀️

Sunlight reflecting off water on a bright dayLight

Reflection: Sometimes energy bounces back.

But what if it doesn't?

Let's follow the energy next.

When Wave Energy Stays Behind

The Wave That Disappeared, or Did It?

Leave a black car in the sun for an hour. Touch the seat. It's burning hot: no fire, no heater, just sunlight hitting dark fabric all afternoon.

🚗 A black car seat gets burning hot in sunlight. The light didn't bounce back; the seat isn't shiny. It didn't pass through; you can't see through it.

🎙️ A recording studio lined with foam is eerily quiet. Sound enters the room and seems to vanish into the walls. Where did it go?

Step 1 Did the energy reflect back off the material? ❌ No: the seat isn't shiny

Step 2 Did the energy transmit through the material? ❌ No: you can't see through it

Step 3 So where did the energy go? Energy can't be destroyed; it must have gone somewhere. → It stayed inside the material

Now we have a word for it

Absorption is what happens when a wave's energy transfers into a material. The wave doesn't bounce back and doesn't pass through; its energy is taken in by the material, usually converted into thermal energy (heat).

🚗Black car seat heating in sunlight

🛣️Black asphalt getting hot on a summer day

🎙️Acoustic foam quieting a recording studio

🏠Carpet absorbing sound; hardwood floors are louder

☀️Solar panels absorbing light and converting it to electricity

👕Wearing dark clothing in summer; absorbs more light energy

Absorption: Sometimes wave energy transfers into the material itself.

But not all energy stays behind.

Sometimes it keeps moving through the material instead.

When Waves Pass Through

The Wave That Kept Going

You're outside at night. Inside the house, the lights are on. You look through the window and see everything inside, clearly, in detail. Light waves traveled from inside, hit the glass, and kept moving, all the way to your eyes.

🪟 Light travels through window glass. The wave keeps moving through solid material and reaches your eyes on the other side.

🚪 A classroom door is closed. You can still hear muffled voices inside. Sound waves passed through the solid wood door.

🤔

Think about it: The energy didn't bounce back. And the glass didn't heat up. So where did the energy go? Make a prediction.

Now we have a word for it

Transmission is what happens when a wave passes through a material. The wave's energy continues moving, through the surface and beyond.

🪟Light through window glass

🚪Sound through a closed door or wall

🌊Sound traveling through water

👓Light through eyeglass lenses

🔬X-rays passing through soft tissue

📻Radio waves passing through walls

Transmission: Some energy passes straight through the material.

But how much gets through isn't the same for every material. Let's compare three different cases.

How Much Gets Through?

Transparent, Translucent, and Opaque

Transmission turns out to exist on a spectrum. Some materials let all the light through. Some let a little through. Some let none through. Watch what happens to a beam of light as it hits three different panels.

👤

Transparent

Light passes through clearly.
Images stay sharp.

Window glass Clear water Eyeglass lens Plastic wrap

👤

Translucent

Some light passes through.
Images look blurry.

Frosted glass Wax paper Fog Stained glass

👤

Opaque

Light cannot pass through.
No image forms.

Brick wall Wooden door Metal Most clothing

Back to the hallway

The window next to the classroom door? Transparent: light fully transmits through. The wooden door? Opaque to light, but only partially opaque to sound, which is why you can still hear voices. The brick wall? Opaque to both.

Quick Recall

Just a quick brain check before we move on. Not graded.

You are back in the hallway. Which material is transparent?

Clear glass Wax paper Brick wall

Important: "Opaque" doesn't mean the energy vanished. It means light can't transmit through; the energy reflects or absorbs instead.

And most real materials do all three things at the same time, just in different proportions.

Let's see what that actually looks like.

Energy Tracker

Where Does the Energy Go?

Real objects almost never do just one thing. Select a material and watch how incoming wave energy divides among the three destinations. The question isn't which behavior; it's how much of each.

Explored

← Select a material above to begin

Did any material put 100% of its energy into just one category?

No. Every single material split its energy among all three destinations. What changes is the ratio.

A mirror mostly reflects. Black asphalt mostly absorbs. Window glass mostly transmits. But none of them does only one thing; they all reflect some, transmit some, and absorb some.

That's the key insight: real materials almost never do just one thing. The difference between them is how much energy goes to each destination.

Wrap-Up

Back to the Hallway

You started this lesson standing in a hallway, wondering why light and sound behaved differently when they reached different materials. Now you know the answer. Every surface reflects, absorbs, and transmits energy. What changes is how much of each happens.

🪟 Window

Light

Mostly transmitted. The glass is transparent; light waves pass through almost completely. That's why you can see the room inside clearly.

Sound

Some transmission, some reflection. Sound gets through more easily near the glass, but not as clearly as through the open door.

🚪 Door

Light

Mostly absorbed and reflected. Wood is opaque; light cannot transmit through. Your eyes see nothing but the door itself.

Sound

Partially transmitted. Some sound energy passes through the wood. That's why you can hear muffled voices, but the door absorbs and reflects most of it.

🧱 Brick Wall

Light

Mostly reflected and absorbed. Very little light transmits through a thick brick wall.

Sound

Almost entirely reflected and absorbed. Very little transmits. The density of brick reflects most sound energy back, and absorbs the rest.

The Answer

A wave can hit an object and still keep moving because transmission is always an option.

When a wave reaches matter, some of its energy can pass straight through; the wave doesn't have to stop.

The Bigger Picture

Most real objects do all three things at the same time.

When a wave reaches matter, its energy is almost always divided among:

Reflected Transmitted Absorbed

What Changes

The ratio. Each material just uses a different mix.

🪟Window glassmostly transmits

🪞Mirrormostly reflects

🛣️Black asphaltmostly absorbs

Quiz

Check Your Understanding

Ten questions covering everything you discovered. Answer every question, then submit.

Your score will not be sent Your score will be sent to your teacher

0 / 10 selected

🔍 The Mystery You Came In With You started this lesson with one question: "How can a wave hit an object and still keep moving?" If you can explain it now, you've solved the mystery.

Wave Behavior

Words You'll Meet

Three Objects. One Question.

Waves Carry Energy: And Energy Has to Go Somewhere

The Wave That Came Back

The Wave That Disappeared, or Did It?

The Wave That Kept Going

Transparent, Translucent, and Opaque

Where Does the Energy Go?

Back to the Hallway

Check Your Understanding

More Learning