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11BT > Waves - Paper 2 > Flashcards

Waves - Paper 2 Flashcards

To revise waves (paper 2)

1
Q

What do waves transfer?

A

Energy

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2
Q

What are the two types of wave?

A

Transverse and longitudinal

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3
Q

Describe a transverse wave

A

The vibrations of the wave are perpendicular to the direction in which energy is transferred.

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4
Q

Give some examples of transverse waves

A

Ripples on a water surface

Any wave in the electromagnetic spectrum

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5
Q

Describe a longitudinal wave

A

The vibrations of the wave are parallel to the direction in which energy is transferred. Longitudinal waves show areas of compression and rarefaction.

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6
Q

Give some examples of longitudinal waves

A

Sound waves

Ultrasound

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7
Q

Define amplitude

A

The amplitude of a wave is the maximum displacement of a point on a wave away from its undisturbed position. It shows us how much energy a wave has.

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8
Q

Define wavelength

A

The wavelength of a wave is the distance from a point on one wave to the equivalent point on the adjacent wave. Measured in meters

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9
Q

Define frequency

A

It is the number of waves that pass a point per second. Measured in hertz (Hz)

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10
Q

Define period (T)

A

Its the time for one exact wave to pass a point. Measured in seconds

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11
Q

State the wave equation with all units

A

wave speed (m/s) = frequency (Hz)× wavelength (m)

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12
Q

Describe an experiment to find the speed of sound through air

A

Measure a distance of 100 m from a wall. Hit two blocks together to make a sound and start timing. Stop timing when the hear the reflected sound (echo). Divide the time recored by 2. use the equation Speed = distance / time

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13
Q

Describe a method to measure the speed of ripples on a water surface.

A

Set up a ripple tank. Find the wavelength by using a ruler to measure across 10 wavelengths. Divide the answer by 10 to find 1 wavelength. Use a stopwatch and count the number of waves produced in 10 seconds. Dived the answer by 10 to find the frequency. Use the equation speed = wavelength x frequency

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14
Q

What can happen to waves when they reach a boundary between two materials?

A

They can be reflected
They can be absorbed (this will cause a small temperature rise)
They can be transmitted (they will pass through)

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15
Q

What is the law of reflection

A

The angle of incident = angle of reflection for a flat plain mirror.

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16
Q

What is refraction?

A

When a wave travels from one medium to another and changes direction.

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17
Q

Why does refraction take place?

A

The change in medium means a change in density which caused a change in speed.

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18
Q

When a substance moves from a more dense to a less dense substance, what is the affect of waves speeds, frequency and wavelength?

A

Wave speed - decreases
Frequency - same
Wavelength - decreases

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19
Q

When a substance moves from a less dense to a more dense substance, what is the affect of waves speeds, frequency and wavelength?

A

Wave speed - increases
Frequency - same
Wavelength - increases

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20
Q

State the normal human hearing range

A

From 20 Hz to 20 kHz

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21
Q

How do we detect sound waves?

A

Within the ear, sound waves cause the ear drum and other parts to vibrate. These vibrations are converting into an electrical signal which is passed onto the brain.

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22
Q

Why do humans have a limited range of frequencies they can detect?

A

The conversion of sound waves to vibrations of solids works over a limited frequency range. This restricts the limits of human hearing.

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23
Q

What is the effect of a louder sound on the ear drum?

A

larger vibrations

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24
Q

What is the effect of a higher pitched sound on the ear drum?

A

Faster vibrations

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25
Q

What is a ultrasound?

A

Ultrasound waves have a frequency higher than the upper limit of hearing for humans (20000 Hz)

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26
Q

How can ultrasound be used for medical and industrial imaging?

A

Ultrasound waves are partially reflected and partially transmitted when they meet a boundary between two different media. The time taken for the reflections to return to the detector can be used to determine how far away such a boundary is.
Distance = speed x time

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27
Q

What are seismic waves

A

Waves produced by Earthquakes

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28
Q

What type of waves are P-waves?

A

longitudinal

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29
Q

What type of waves are S-waves?

A

Transverse

30
Q

Which earthquake wave scant travel through the liquid core?

A

S-waves as they are transverse

31
Q

What is a shadow zone?

A

An area where no p waves or s waves are detected

32
Q

What does a shadow zone show us?

A

There must be a liquid core because:
P waves are refracted at the core mantle boundary
S waves can’t travel through the liquid core

33
Q

State the waves that make up the electromagnetic spectrum, in order of increasing wavelength

A 
Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays
34
Q

What do all electromagnetic waves have in common?

A

They are all transverse waves
They can all travel through a vacuum
They all travel at the speed of light through a vacuum

35
Q

How are radio waves produced?

A

By an oscillating electrical current.

36
Q

What happens when radio waves are absorbed by an aerial?

A

When radio waves are absorbed they may create an alternating current with the same frequency as the radio wave itself

37
Q

What are the dangers of ultraviolet waves

A

Can age skin prematurely
Can burn skin which can lead to skin cancer
Damage eyes which can lead to blindness

38
Q

What are the dangers of X-rays and gamma rays?

A

X-rays and gamma rays are ionising radiation
Low doses can damage DNA and cause cancer
Large doses can kill cells

39
Q

State some uses of radio waves

A

television and radio, these waves stay within the earths atmosphere.

40
Q

State some uses of microwaves

A

Satellite communications eg mobile phone and satellite TV. Microwaves can travel to space and back.
Cooking food.

41
Q

State some uses of infrared

A

electrical heaters, cooking food, infrared cameras

42
Q

State some uses of visible light

A

fibre optic communications

43
Q

State some uses of ultraviolet

A

energy efficient lamps, sun tanning

44
Q

State some uses of X-rays and Gamma rays

A

medical imaging and treatments.

45
Q

How does a lens work?

A

A lens forms an image by refracting light to a focal point

46
Q

When describing the nature of an image formed the key words to use are?

A

Real or virtual
Magnified or diminished
Upright or inverted

47
Q

What are the units of magnification

A

no units as it is a ratio

48
Q

In a ray diagram the symbol for a convex lens will be represented by?

A

A vertical line with arrow heads at each end

49
Q

In a ray diagram the symbol for a concave lens will be represented by?

A

A vertical line with inverted arrow heads at each end

50
Q

Describe specular reflection

A

Reflection from a smooth surface in a single direction is called specular reflection

51
Q

Describe diffuse reflection

A

Reflection from a rough surface causes scattering: this is called diffuse reflection.

52
Q

Explain how a red filter works

A

A red filter will allows the red wavelength to be transmitted whilst the wavelengths of all the other colours will be absorbed.

53
Q

Describe how we can see a blue object.

A

A blue object will reflect treble wavelengths into our eyes. All the other wavelengths and colours will be absorbed.

54
Q

Describe how we can see a white object.

A

If all wavelengths are reflected equally the object appears white.

55
Q

Describe how we can see a black object.

A

If all wavelengths are absorbed the objects appears black.

56
Q

Objects that transmit light are called?

A

transparent or translucent

57
Q

What is the relationship between the temperature of an object and the amount of infrared radiation it emits?

A

The hotter the body, the more infrared radiation it radiates in a given time.

58
Q

Describe a perfect black body

A

A perfect black body is an object that absorbs all of the radiation incident on it. A black body does not reflect or transmit any radiation. Since a good absorber is also a good emitter, a perfect black body would be the best possible emitter.

59
Q

How can a body be at a constant temperature?

A

A body at constant temperature is absorbing radiation at the same rate as it is emitting radiation.

60
Q

How can the temperature of a body increase?

A

The temperature of a body increases when the body absorbs radiation faster than it emits radiation.

61
Q

How can the temperature of a body decrease?

A

The temperature of a body decreases when the body absorbs radiation slower than it emits radiation.

62
Q

What factors affect the temperature of the Earth?

A

The temperature of the Earth depends on many factors including: the rates of absorption and emission of radiation, reflection of radiation into space.

63
Q

When light slows down which direction does it refract?

A

Towards the normal

64
Q

When light speeds up which direction does it refract?

A

Away from the normal

65
Q

What surface is the best emitter of infrared radiation?

A

Matt black surfaces

66
Q

What surface is the worst emitter of infrared radiation?

A

Silver (shiny) surfaces

67
Q

What surface is the best absorber of infrared radiation?

A

Matt black surfaces

68
Q

If an object’s temperature is higher, what will happen to the infrared radiation it’s emitting?

A

Higher temperature -> more infrared radiation emitted in a given time

69
Q

Explain why light refracts as it passes from air into glass?

A

As light moves from air into glass it slows down.
The edge of the wave front entering the glass first slows down first
Part of the wave front that is still in the sir continues at a higher speed causing a change in direction

70
Q

Describe how x-rays are used for medical imaging

A

pass through soft tissue

but are absorbed by bone

11BT (18 decks)

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