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Physics > Waves > Flashcards

Waves Flashcards

1
Q

What are waves

A

Waves are a way of transferring energy and information without transferring matter

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2
Q

What are the two types of waves

A

Transverse waves and longitudinal waves

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3
Q

What is a transverse wave

A

A transverse wave is a wave whose oscillations are perpendicular to the direction of motion

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4
Q

What is the crest of a wave

A

The crest of a wave is the point where the particles are at the top of their oscillation

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5
Q

What is the trough of a wave

A

The trough of a wave is the point where the particles are at the bottom of their oscillation

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6
Q

Give some examples of transverse waves

A

All waves of the Electromagnetic spectrum (radio waves, microwaves)
Secondary seismic waves

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7
Q

What is a longitudinal wave

A

A longitudinal wave is a wave whose oscillations are parallel to the direction of motion

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8
Q

What are the compressions of a wave

A

Compressions are high pressure areas where particles are close to each other

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9
Q

What are the rarefactions of a wave

A

Rarefactions are low pressure areas where particles are further apart

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10
Q

Give some examples of longitudinal waves

A

Sound waves
Primary seismic waves

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11
Q

What is the amplitude of a wave

A

The amplitude of a wave is the maximum displacement from equilibrium (measured in m)

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12
Q

What is the wavelength of a wave

A

The wavelength is the distance between a particular point on a wave and the same point on the next wave

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13
Q

Define frequency

A

Frequency is the number of waves produced each second

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14
Q

Give the equation for frequency

A

Frequency (Hz) = number of waves/time

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15
Q

Define the time period

A

Time period is the time taken for one complete oscillation

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16
Q

State the equation that links frequency with time period

A

Frequency = 1 / time period

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17
Q

A generator produces 48 waves in 12 seconds. Calculate the frequency of the waves

A

f = w / t
f = 48 / 12
f = 4 Hz

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18
Q

A generator produces 48 waves in 12 seconds. Calculate the time period of the wave

A

f = 4 Hz
T = 1 / f
T = 1 / 4
T = 0.25s

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19
Q

What is a wavefront

A

A wavefront is a line on a wave where all vibrations are on the same position

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20
Q

State the equation for wave speed

A

Wave speed = frequency(Hz) * wavelength(m)

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21
Q

What is the speed of a wave with a frequency of 2.5kHz and wavelength of 50 cm

A

s = f * λ
s = 2500 * 0.5
s = 1250 m/s

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22
Q

What is the doppler effect

A

The doppler effect is the apparent change in the frequency of a wave caused by the relative motion between the source and the observer

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23
Q

Explain how the sound heard by a student throwing a buzzer away from him changes

A

The sound heard from the student changed due to the doppler effect. As the buzzer started to move away, the observed wavelength increased, the wavefronts were further apart and the frequency decreased, while the wave speed remained constant

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24
Q

What are mechanical waves

A

Mechanical waves are waves that require a medium in order to propagate. They cannot transmit energy through vacuum

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25
Q

Give some examples of mechanical waves

A

Sound waves
Water waves

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26
Q

What are electromagnetic waves

A

Electromagnetic waves are waves that can transmit energy through vacuum. They do not require a medium in order to propagate

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27
Q

What separates the waves of the electromagnetic spectrum

A

The waves of the electromagnetic spectrum are separated by their different wavelengths and frequencies

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28
Q

What is the color spectrum of visible light waves called

A

ROYGBIV
Red
Orange
Yellow
Green
Blue
Indigo
Violet

29
Q

Name all the waves of the electromagnetic spectrum in terms of increasing frequency

A

radio waves
microwaves
infrared waves
visible light waves
ultraviolet waves
x-rays
gamma rays

30
Q

What are the common properties of electromagnetic waves

A

They carry energy and information
They are transverse waves
They can travel through vacuum at the speed of light
They can all be reflected and refracted

31
Q

What are the uses and dangers of Gamma rays

A

Uses: They are used to sterilize equipment as they can kill bacteria
Dangers: Mutation of DNA can cause cancer

32
Q

What are the uses and dangers of X-rays

A

Uses: Observing internal structures of objects and materials as they can penetrate soft tissues but not bones
Dangers: Mutation of DNA can cause cancer

33
Q

What are the uses and dangers of Ultraviolet waves

A

Uses: Detecting security ink as it fluoresces with UV light
Dangers: Blindness

34
Q

What are the uses and dangers of Visible light waves

A

Uses: Optical fibres as they can undergo total internal reflection
Dangers: High intensity light can damage eyes

35
Q

What are the uses and dangers of Infrared waves

A

Uses: Optical fibres as they can undergo total internal reflection
Dangers: Skin burns

36
Q

What are the uses and dangers of Microwaves

A

Uses: Satellite communication because they can penetrate the Earth’s atmosphere
Dangers: Internal heating of body tissue

37
Q

What are the uses and dangers of Radiowaves

A

Uses: Long range communication because they can be reflected from the Earth’s atmosphere
Dangers: Radio waves have no danger :)

38
Q

What are luminous objects

A

Luminous objects are objects that emit their own light

39
Q

What are non-luminous objects

A

Non-luminous objects are objects that do not emit their own light

40
Q

Give two examples of luminous and non-luminous objects

A

Luminous: Sun, light bulbs
Non-luminous: desks, walls

41
Q

What does the law of reflection state

A

The law of reflection states that when a light ray strikes a plane mirror, it is reflected so that the angle of incidence is equal to the angle of reflection

42
Q

Which angle is the angle of incidence

A

The angle of incidence is always the angle between the incident ray and the normal

43
Q

What is the normal line

A

The normal is an imaginary line drawn perpendicular to the plane mirror

44
Q

What is refraction

A

Refraction is the change in the direction of a wave at the boundary between two media due to a change in speed

45
Q

What happens when light enters a more dense medium

A

When light enters a more dense medium, it slows down and bends towards the normal

46
Q

What happens when light enters a less dense medium

A

When light enters a less dense medium, it speeds up and bends away from the normal

47
Q

What happens if the incident ray strikes the boundary between two media at 90 degrees

A

The ray will continue without a change of direction. This is because the angle of incidence is 0, so the angle of refraction will be also 0

48
Q

State three ways in which light waves change as they pass into another medium

A

Change of speed
Change of direction
Wavelength decreases

49
Q

What is the refractive index

A

The refractive index is a number that expresses the ability of a medium to bend light

50
Q

What is the refractive index of water

A

1.3

51
Q

What is the refractive index of glass

A

1.5

52
Q

State the equation used to calculate the refractive index of a medium

A

n = sin i / sin r
*this can only be used when traveling from air to a denser medium

53
Q

Describe the experiment used to calculate the refractive index of a glass block

A

Shine a ray of light through a glass block using a light box. Mark the positions of the incidence and refracted rays on the piece of paper and draw the refracted ray using a pencil. Using a protractor, measure the angle of incidence and the angle of refraction. Repeat this for many different values of the refractive index. Then she should find the sine of the two values and calculate their ratios by diving the sine of the angle of incidence with the sine if the angle if refraction in order to find the refractive index. She could also plot a graph with the values of sin i and sin r and measure the gradient to find the refractive index

54
Q

What is total internal reflection

A

Total internal reflection is the total reflection of light that occurs when moving from an area of high density to one of low density, while the angle of incidence is bigger than the critical angle

55
Q

What is the critical angle

A

The critical angle is the angle of incidence that offers an angle of refraction of 90 degrees

56
Q

What is the equation for the critical angle

A

sin c = 1 / n

57
Q

What is total internal reflection used for

A

Binoculars
Optical fibres
Periscopes

58
Q

What do optical fibres do

A

Optical fibres use total internal reflection to contain and guide light

59
Q

Give two uses for optical fibres

A

Fibre broadband sends computer information coded as pulses of light along underground optical fibres
Doctors can look at the inside of their patients using an endoscope

60
Q

What is dispersion

A

Dispersion occurs when white light passes through a prism and emerges out as a band of different colors

61
Q

Why does dispersion occur

A

Dispersion occurs because the different colors of white light travel in the glass prism at different speeds, and they thus are refracted by different amounts

62
Q

What is the human audible range

A

20Hz - 20000Hz

63
Q

What are ultrasound waves

A

Waves above the audible range

64
Q

What are infrasound waves

A

Waves below the audible range

65
Q

What does the loudness of a sound depend on

A

The amplitude

66
Q

What does the pitch of a sound depend on

A

The frequency

67
Q

What do we use to display a sound wave

A

An osciloscope

68
Q

How does SONAR work

A

SONAR helps calculate the depth of water. Sound pulses are emitted towards the seabed, they reflect and their echo is received. The time between emission and return of the echo is recorded. Since we know both the time and the speed of sound in water we can calculate its depth

Physics (7 decks)

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