Sound and Light: Vibrations, Shadows and Mirrors
A drum, a bell and your voice all make sounds. A window lets light in, but a wall does not. Let’s find out how sounds are made and what happens when light meets different things.
This lesson takes about 15 minutes. You can take a break after each part.
Before you start
Learning objectives
- I can show that a sound is made by something that vibrates.
- I can show that a sound can make things vibrate.
- I can sort things that let light through, let some light through, or stop the light.
- I can use a mirror to send light another way.
Sounds come from vibrations
What is a vibration?
When something vibrates, it moves back and forth very fast. A plucked guitar string vibrates. A drum skin vibrates when you tap it.
No vibration, no sound
Every sound is made by something that vibrates. Put your hand on your throat and hum: you can feel it vibrate. When the vibration stops, the sound stops.
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Sound can make things vibrate
Sound can move things
A sound can make other things vibrate. Very loud music can make a window or a table shake a little.
The dancing rice
Put a few grains of rice on a drum. Bang a second drum close to it. The sound makes the first drum skin vibrate, and the rice jumps.
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Light passes through, or not
Three kinds of materials
Transparent things, like clear glass, let almost all the light through: you see clearly through them. Translucent things, like wax paper, let some light through. Opaque things, like cardboard or wood, stop the light.
Shadows
When an opaque thing stops the light, there is a dark place behind it: a shadow. A shadow is not a thing. It is where the light cannot reach.
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Mirrors send light back
Light bounces off a mirror
A mirror is shiny. When light hits a mirror, it bounces off and goes another way. A mirror does not make light: it sends back light from a lamp or the Sun.
Changing the path of light
You can turn a mirror to send light where you want, even around a corner or behind a box.
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Review game
Final assessment
To master the lesson, you need at least 60% correct answers.
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Summary
- A sound is made by something that vibrates; stop the vibration and the sound stops.
- A sound can make other things vibrate, like rice on a drum.
- Transparent things let almost all the light through, translucent things let some through, opaque things stop it.
- A shadow is where an opaque thing stops the light.
- A mirror makes light bounce off and change direction.
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