Sound
Practice Test-1
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Quick questions:
1.
Use the words in the box to fill in the gaps in the paragraph below:
vacuum
liquids
wave
Total marks=25
[4]
vibrations
Sound is made by …………………………………………………. Sound can travel through all solids, …………………………………………………. and gases. Sound
travels through the air as a …………………………………………………. when the particles of air push each other. Sound cannot travel
through a ………………………………………………….
2. What do we call the substance sound travels through?
[2]
3. Why can't sound travel through a vacuum?
[2]
[1]
4. What is an echo?
[2]
5. Copy and complete the following sentences about using echoes.
Submarines can use sonar to find out how deep water is. Sound waves are sent down to the bottom of the sea.
When they hit the sea bed the waves …………………………………………………. The distance the wave has travelled can be calculated
by measuring the …………………………………………………. between sending out the wave and receiving its echo.
6. In the slinky spring model of a sound wave, each coil vibrates backwards and forwards but goes back to its
original position.
[4]
What does this show about how sound travels through air?
(a) The sound source makes the air next to it vibrate and this air passes on the vibration.
(b) Only the air next to a sound source vibrates.
(c) The particles in air do not move in any regular pattern.
(d) Air moves forwards from the sound source to where it is detected.
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Connect Your understanding:
[2x5=10]
7. The apparatus shown on that the right is often used to prove that sound
cannot travel through a vacuum.
(a) Why does this experiment prove that sound cannot travel through a vacuum?
(b) Explain why sound cannot travel through a vacuum.
8. The warmer air is, the further apart the air particles are likely to be.
Do you think the speed of sound through warm air would be faster or slower than through cold air?
9. There is no atmosphere on the Moon. Explain why, even if we were very close, we could not hear an explosion
that happened on the Moon.
10. A girl sees the lightning in a thunderstorm 8 seconds before she hears the thunder. If sound travels at 340
m/s in air, how far away is the thunderstorm?
11. A boy is standing 400 m away from a cliff. He makes a loud noise. If sound travels at 340 m/s, how long will it
be before he hears the echo? Show your working.
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Sound
Practice Test-1
•
1.
Total marks=25
Answer the following:
Sound A: 400 Hz
Sound B: 200 Hz
Sounds A and B are played equally loudly.
a) For someone listening to the two sounds, how would B compare with A?
b) Which sound has the longer wavelength?
2. A microphone picks up three different sounds, X, Y, and Z, one after another. Here are their waveforms on
the screen of an oscilloscope:
a) Which sound has the greatest amplitude?
b) Which sound is the loudest?
c) Which sound has the highest frequency?
d) Which sound has the highest pitch?
3. Use the wave equation to work out the following (assume that the speed of sound in air is 330 m s):
a) The wavelength of a sound whose frequency is 660 Hz.
b) The frequency of a sound whose wavelength is 2m.
4. Two of the strings on a guitar can be used to play two different sounds.
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Sound 1 is produced by playing a string that vibrates 300 times in 2 seconds.
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Sound 2 is produced by playing a string that vibrates 1000 times in 5 seconds.
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The amplitude of the two sounds was measured, and sound 1 had an amplitude which was twice that of sound 2.
a) Which sound was the loudest?
b) Which sound had the highest frequency?
c) which sound had the longest wavelength?
d) Which sound had the lowest pitch?
5. Figure 11.4 shows the oscilloscope traces for sounds D, E and F. You should use these traces to answer
questions 2 and 3.
a) Which of the sounds is the loudest? How do you know?
b) Which has the highest pitch? How do you know?
c) Will shortening a guitar string make the pitch of the note higher or lower? Explain your answer.
6. Which of the animals dogs, cats, dolphins and bats:
a) can hear the lowest frequency?
b) can hear the highest frequency?
c) can hear over the biggest range of frequencies?
7. Why can very high-pitched sounds hurt you and possibly damage your hearing?
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