7th grade light, sound and waves

Question 1

You see lightning and hear the thunder 2 seconds later. Sound travels at about 340 m/s. About how far away is the storm, in metres?

Answer m

Question 2

Why does sound travel faster in steel than in air?

• A. Air has no particles
• B. Sound is magnetic
• C. Steel is shiny
• D. Particles in solids are close together and strongly linked, so vibrations pass on quickly

Question 3

Sound travels at about 340 m/s in air. How far does it travel in 4 s, in m?

Answer m

Question 4

A pencil in a glass of water looks bent. Why?

• A. The water bends the pencil
• B. Light reflects off the water
• C. Light refracts (changes direction) as it passes from water to air
• D. The glass is curved

Question 5

Colour and light: which statement is NOT true?

• A. Black objects absorb most of the light that falls on them.
• B. White light is a mixture of colours.
• C. Light travels at the same speed in glass as in air.
• D. Light slows down when it enters glass or water.

Question 6

How sound travels: which statement is NOT true?

• A. Sound cannot travel through a vacuum.
• B. In a sound wave, air particles travel all the way from the source to your ear.
• C. Sound waves are longitudinal.
• D. Whales can communicate over long distances underwater.

Question 7

In which material does sound travel fastest?

• A. steel
• B. a vacuum
• C. air
• D. water

Question 8

You shout towards a cliff and hear the echo 2 s later. Sound travels at 340 m/s. How far away is the cliff, in metres?

Answer m

Question 9

You see lightning and hear the thunder 4 seconds later. Sound travels at about 340 m/s. About how far away is the storm, in metres?

Answer m

Question 10

In which direction do air particles vibrate when a sound wave passes?

• A. up and down, at right angles to the wave
• B. in circles
• C. backwards and forwards, parallel to the direction the sound travels
• D. they do not move

Question 11

Sound travels at about 1500 m/s in water. How far does it travel in 2 s, in m?

Answer m

Question 12

What colour does a green leaf look under only red light?

• A. green
• B. red
• C. white
• D. black (very dark)

Question 13

Colour and light: which statement is NOT true?

• A. White light is a mixture of colours.
• B. Light slows down when it enters glass or water.
• C. A red filter turns white light red by adding red.
• D. A red filter lets red light through and absorbs other colours.

Question 14

How sound travels: which statement is NOT true?

• A. Sound travels fastest in gases.
• B. Whales can communicate over long distances underwater.
• C. Sound cannot travel through a vacuum.
• D. Sound travels faster in water than in air.