Light vs Sound Waves

Light and Sound Waves: How They Behave and Interact with Matter

By NaaJah Richardson

What Are Waves?

• Waves carry energy from one place to another.

• Two main types: Light waves and Sound waves

• Light = electromagnetic wave (can travel through space)

• Sound = mechanical wave (needs a medium)

Vocabulary

• Light – electromagnetic energy that we can see

• Sound – vibrations that travel through a medium to our ears

• Media (plural of medium) – materials that waves travel through (air, water, solids)

​​Light wave

​​Sound wave

Property	Light Wave	Sound Wave
Type	Electromagnetic	Mechanical
Needs a Medium?	No	Yes
Speed	Very fast (in a vacuum)	Slower than light
Can Travel in Space?	Yes	No

• Waves bounce off a surface.

• Light reflects off mirrors or shiny surfaces.

• Sound reflects as echoes.

• Example: Shouting in a canyon or looking into a mirror.

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​Reflection

• Waves bend as they pass through different media.

• Light bends when it enters water or glass.

• Sound changes speed in different materials.

• Example: A straw looks bent in a glass of water.

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​Refraction

• Waves spread out when they go through an opening or around an obstacle.

• Both light and sound can diffract.

• Example: Hearing someone talking around a corner.

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Diffraction

​Light travels faster than sound.

• Speed depends on the medium:

  • Light: Fastest in a vacuum

  • Sound: Fastest in solids

• Example: You see lightning before you hear thunder.

​Speed

Multiple Choice

This wave requires a medium.

• Light

• Sound

• Both

Multiple Choice

This wave transfers energy from one place to another.

• Light

• Sound

• Both

Multiple Choice

This wave can travel through empty space

• Light

• Sound

• Both

How Waves Interact with Matter

• Absorption – Wave energy is taken in (e.g., dark colors absorb more light)

• Reflection – Wave bounces back

• Transmission – Wave passes through (like light through glass)

​light passes through completely (clear glass)

​​Transparent

​some light passes through (frosted glass)

​​Translucent

​no light passes through (wood, metal)

​​Opaque

​Quick Review

• Light = electromagnetic Sound = mechanical

• Both reflect, refract, diffract

• Speed and behavior depend on the medium

• Waves can be absorbed, reflected, or transmitted

Multiple Choice

When light waves bounce off a surface we call this:

• Reflection

• Refraction

• Absorption

Multiple Choice

Light waves bouncing off of this mirror is an example of:

• Reflection

• Refraction

• Absorption

Multiple Choice

A black shirt capturing light waves and making a person feel hot in the summer is an example of:

• Reflection

• Refraction

• Absorption

Multiple Choice

When you place things into water they sometimes look bent (see the image below). What is this an example of?

• Refraction

• Diffraction

• Transmission

• Absorption