Physics-11 Sound

When the oscillations are ​ (a)   or from side to side like those above, the waves are called ​ (b)   . In transverse waves, the ​ (c)   are at ​ (d)   to the direction of travel.

• up and down
• transverse waves
• oscillations
• right-angles

Answer explanation

When the oscillations 振荡 are up and down or from side to side like those above, the waves are called transverse waves 横波. In transverse waves, the oscillations are at right-angles to the direction of travel.

In physics, a transverse wave is a wave whose oscillations are perpendicular to the direction of the wave's advance. This is in contrast to a longitudinal wave which travels in the direction of its oscillations. Water waves are an example of transverse wave.

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Click on the longitudinal wave:

Answer explanation

When the oscillations 振荡 are up and down or from side to side like those above, the waves are called transverse waves 横波. In transverse waves, the oscillations are at right-angles to the direction of travel.

Moving the end coil of the spring backwards and forwards also produces compression 压缩区 and rarefaction 稀疏区. When the oscillations are backwards-and-forwards like those above, the waves are called longitudinal waves 纵波. In longitudinal waves, the oscillations are in the direction of travel.

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The ​ (a)   ​ of the waves is measured in metres per second (m/s).

​ (b)   This is the number of waves passing any point per second. The 

SI unit of _____ is the ​ (c)   .

​ (d)   This is the distance between any point on 

a wave and the equivalent point on the next.

​ (e)   This is the maximum distance a point moves 

from its rest position when a wave passes.

• speed
• Frequency
• hertz
• Wavelength
• Amplitude

Answer explanation

Speed 波速 The speed of the waves is measured in metres per second (m/s).

Frequency 频率 This is the number of waves passing any point per second. The 

SI unit of frequency is the hertz (Hz) 赫兹.

Wavelength 波长 This is the distance between any point on 

a wave and the equivalent point on the next.

Amplitude 振幅 This is the maximum distance a point moves 

from its rest position when a wave passes.

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What is the Frequency if the wavelength is 3 meters and the speed is 15m/s

(answer is in hertz)

Mathematical Equivalence

ON

Answer explanation

f=v/λ

F=frequency

V=velocity

λ=wavelength

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Sound waves are ​ (a)   . The air ​ (b)   backwards and 

forwards as the compressions and ​ (c)   pass through it. When a 

compression passes, the air pressure rises. When a rarefaction passes, the pressure falls. The distance from one compression to the next is the ​ (d)   .

• longitudinal waves
• oscillates
• rarefactions
• wavelength

Answer explanation

Sound waves are longitudinal waves. The air oscillates backwards and 

forwards as the compressions and rarefactions pass through it. When a 

compression passes, the air pressure rises. When a rarefaction passes, the pressure falls. The distance from one compression to the next is the wavelength 波长.

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The material in which a sound waves travel is called the ______.

• medium

• vacuum

• frequency

• amplitude

Answer explanation

Sound waves need a material to travel through. This material is called 

a medium 介质. Without it, there is nothing to pass on any oscillations. Sound cannot travel through a vacuum 真空 (completely empty space).

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Sound cannot travel through a _____>

Answer explanation

Sound waves need a material to travel through. This material is called 

a medium 介质. Without it, there is nothing to pass on any oscillations. Sound cannot travel through a vacuum 真空 (completely empty space).

Match the following

• cannot travel through this

• solid

• faster

• gas

• fastest

• vacuum

• fast

• liquid

Answer explanation

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The number of oscillations per second is called the ​ (a)   . It is measured 

in ​ (b)   (Hz) 赫兹. 100 Hz=100 oscillations in one second

Different frequencies sound different to the ear. You hear high frequencies 

as high notes: musicians say that they have a ​ (c)   高音调. You hear low

frequencies as low notes: they have a ​ (d)   低音调.

• frequency
• hertz
• high pitch
• low pitch

Answer explanation

The number of oscillations per second is called the frequency. It is measured 

in hertz (Hz) 赫兹. 100 Hz=100 oscillations in one second

Different frequencies sound different to the ear. You hear high frequencies 

as high notes: musicians say that they have a high pitch 高音调. You hear low

frequencies as low notes: they have a low pitch 低音调.

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The ​ (a)   on the ​ (b)   is a graph showing how the air pressure varies with time as the sound waves enter the ​ (c)   . The horizontal line is the time axis.

• waveform
• oscilloscope
• microphone

Answer explanation

The waveform 波形 on the oscilloscope 示波器 is a graph showing how the air pressure varies with time as the sound waves enter the microphone. The horizontal line is the time axis.

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