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Physics Theory > Ch12 Sound > Flashcards

Ch12 Sound Flashcards

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1
Q

Why are sound waves sometimes referred to as pressure waves?

A

The vibrations of the sound source cause a regular variation in the pressure of the medium.

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2
Q

What is the audible range of frequencies for humans?

A

Between 20 and 20 000 hertz

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3
Q

Why can’t sound waves propagate through a vacuum?

A

Sound is a mechanical wave, which means it need a medium to travel (propagate) through. A vacuum is an empty space with no particles so it isn’t possible for sounds to travel through because there are no particles to carry the vibrations.

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4
Q

Define compressions:

A

A region of a sound wave where the particles are pushed together
Regions of high pressure

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5
Q

Define rarefactions:

A

A region of a sound wave where the particles are further apart
Regions of low pressure

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6
Q

Define amplitude:

A

The biggest height/depth of a wave from its undisturbed position

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7
Q

Define frequency:

A

The number of complete vibrations/waves per unit time

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8
Q

Define hertz:

A

The unit o frequency
1Hz = 1 wave per second

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9
Q

Define ultrasound:

A

Any sound with a frequency higher than 20 000 Hz

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10
Q

Why are sound waves longitudinal?

A

The vibrations create compressions and rarefractions which creates pressure changes
The air particles vibrate parallel to the direction of propagation.

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11
Q

What are 3 factors affections the speed of sound?

A

1) density of the medium
2) temperature of the medium
3) pressure of the medium

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12
Q

Why do sound waves travel faster through solids than liquids or gasses?

A

Denser mediums → sound waves → travel more quickly → their particles are closer together

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13
Q

Why do sound waves travel faster through a medium with a higher temperature?

A

The higher the temp of medium → faster the particles move → more kinetic energy → quicker sound can travel through the medium faster

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14
Q

How does pressure influence the speed of sound waves?

A

The more pressure in medium → closer particles are in medium → faster sound can travel through

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15
Q

Define echo:

A

Echoes are reflected sounds from surrounding objects

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16
Q

What is a similarity and difference between the echo and the original sound?

A

They have the same characteristics but travel in opposite directions

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17
Q

What does sonar stand for?

A

Sound Navigation And Ranging

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18
Q

Define echolocation:

A

A technique used by some animals to detect the location of their surrounding obstacles by using reflected sound

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19
Q

What are the shapes of waves called?

A

Waveforms

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20
Q

What does an oscilloscope do?

A

It is a voltmeter that changes electrical signals into visual traces on the screen
The visual trace is actually a graph of voltage against time

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21
Q

Define the period(T) of a wave:

A

The length of time that it takes for one complete cycle (wave) to pass a fixed point

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22
Q

What is the symbol for frequency?

A

f

23
Q

Define frequency:

A

The number of complete cycles (waves) passing a fixed point per second

24
Q

What is the equation for frequency?

A

f=1/T

25
Q

What is the equation for the period of a wave?

A

T=1/f

26
Q

What is the unit for frequency?

A

hertz (Hz)

27
Q

What does the amplitude of a sound wave determine?

A

The Volume/Loudness

28
Q

What does a bigger amplitude mean:

A

Louder sound

29
Q

What does a smaller amplitude mean:

A

Softer sound

30
Q

What does the volume of a sound depend on?

A

1) Amplitude of a sound wave
2) Whether its frequency lies in a region where the ear is more/less sensitive

31
Q

What does the frequency of a wave determine?

A

The pitch

32
Q

What does a higher frequency mean?

A

A higher pitch

33
Q

What does a lower frequency mean?

A

A lower pitch

34
Q

Define infrasound:

A

Sounds w a frequency lower than 20Hz

35
Q

Define ultrasound:

A

Sounds with a frequency higher than 20 000Hz

36
Q

What animals use infrasound to communicate?

A

Whales
Alligators

37
Q

What animals use ultrasound for echolocation?

A

Dolphins
Bats

38
Q

How does ultrasound to form images work?

A

When ultrasound is sent through the body and it reaches the boundary between 2 different mediums (difference in substance like bodily fluid and muscle) part of the wave is transmitted through the next medium and another part is reflected.
The reflected waves are detected and electronically combined to form an image of the region

39
Q

What are the benefits of using ultrasound in medicine?

A

It is a safe and non-invasive way of scanning the body

40
Q

What are 2 characteristics of ultrasound waves:

A

1) High frequency
2) Very short wavelengths

41
Q

Define a longitudinal wave:

A

The direction of the disturbance, that is the direction in which the particles in the medium vibrate, is parallel to the direction of propagation of the wave.

42
Q

How would you calculate how far away a storm is?

A

Find the time between the lightning and thunder and devide by 3.
→ sound travels 1km in about 3 seconds

43
Q

What is the speed of sound in air?

A

Between 330 m/s and 350 m/s

44
Q

Why is there barely an echo in a classroom but outside might be more of an echo?

A

In a classroom the objects that the sound reflect of are nearby so the echo will be so close to the original sound, you wont even hear it.
Outside the sound has to travel a lot further so you may hear an echo

45
Q

Define wavelength:

A

The distance between 2 successive points that are exactly in phase
Ex. Between 2 successive troughs/crests

46
Q

Define pulse:

A

A single disturbance that is propagated from one point to another in a medium

47
Q

Define medium:

A

A substance through which a disturbance travels

48
Q

Define propagate:

A

Process by which a disturbance travels through a medium

49
Q

Define equilibrium position:

A

Rest position of the medium where there is no disturbance

50
Q

Define superposition:

A

Superposition of waves is the addition of the disturbances (amplitudes) of the 2 pulses that occupy the same space at the same time

51
Q

Define interference:

A

When 2/more pulses/waves move through the same space at the same time, as they overlap the phenomena of interference can be observed

52
Q

What are the 2 types of interference?

A

1) constructive interference
2) destructive interference

53
Q

Define constructive interference:

A

When 2 pulses amplify each other to result in a single pulse with a greater amplitude

54
Q

Define destructive interference:

A

When 2 pulses weaken/canceleach other and result in a single pulse with a smaller amplitude/no pulse

Physics Theory (14 decks)

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