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waves Flashcards

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1
Q

what is a transverse wave?

A

a wave for which oscillations are perpendicular (at 90*) to the direction of energy transfer

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2
Q

what is a longitudinal wave?

A

a wave for which the oscillations are parallel to the direction of energy transfer

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3
Q

give examples of transverse waves

A

-all electromagnetic waves (EMWs)
-ripples and waves in water (wave travels, not water)
-a wave on a string
-seismic s-waves

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4
Q

give examples of longitudinal waves

A

-sound waves (wave not air travels)
-seismic p-waves

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5
Q

what is wave speed and its equation?

A

the speed at which energy is transferred through a medium
-wave speed = frequency (Hz) x wavelength (m)

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6
Q

what is wavelength?

A

the distance from a point on a wave to the same point on the adjacent wave (e.g. peak to peak/trough to trough)

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7
Q

what is the frequency of a wave?

A

the number of waves that pass a given point each sec, measured in hertz (Hz)

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8
Q

what is a wave’s amplitude?

A

the maximum displacement of a point on the wave from its undisturbed position

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9
Q

how do sound waves travel through a solid? (HIGHER)

A

the particles in the solid vibrate and transfer kinetic energy through the material

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10
Q

what is the frequency range of human hearing?

A

20Hz-2kHz

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11
Q

how do humans hear sound?

A

-Within the ear, sound waves cause the ear drum and other parts to vibrate which causes the sensation of sound.
-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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12
Q

do sound waves travel faster in solids or gases? why?

A

sound waves travel faster in solids because the particles are closer together so vibrations pass through the solid easier

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13
Q

describe the relationships between frequency, amplitude and sound

A

-high frequency = high pitch
- low frequency = low pitch
- small amplitude = quiet sound
- large amplitude = loud sound

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14
Q

can sound waves pass through a vacuum? why?

A
  • sound waves only travel through mediums e.g. air, solid because they pass through particles vibrating
  • cannot pass through a vacuum as there are no particles
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15
Q

what are ultrasound waves?

A

waves which have a frequency higher than the upper limit of human hearing (20kHz)

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16
Q

give an example + describe a use of ultrasound waves

A

medical imaging –> safer than x-rays as does not increase risk of cancer
industrial imaging–>finds flaws in objects such as pipes/materials e.g. wood or metal

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17
Q

what natural event causes seismic waves to be produced? what types are produced?

A

-earthquakes
-seismic s-waves and p-waves are produced

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18
Q

state a difference between the mediums that P-waves and S-waves can travel through?

A
  • P-waves travel through both solids and liquids
  • S-waves only travel through solids (not liquids)
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19
Q

what do both p-waves and s-waves provide evidence for?

A

evidence for the structure and size of the Earth’s core

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20
Q

what technique is used to detect objects in deep water and measure water depth?

A

-echo sounding
-high frequency sound waves are emitted, reflected and detected
-time difference between emission and detection, alongside wave speed, are used to measure distances (s = v x t)

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21
Q

what is the method to measure the speed of sound in air?

A
  • Make a noise at ~50m from a solid wall, and record time for the echo to be heard.
  • then use speed = distance/time
  • flawed because values recorded will be dependant on reaction time of the observer; will not be entirely accurate
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22
Q

what is the method for measuring waves in a ripple tank? (practical)

A
  1. set up the apparatus and fill the ripple tank with water to a depth of 1cm
  2. turn on the power supply and the light source to produce a wave pattern on the screen
  3. wavelength can be found by using a ruler to measure the length of the screen and dividing this distance by the number of wavefronts
  4. frequency determined by counting the number of waves that passes a point in ten seconds then divide by 10
  5. record the measurements and repeat to find an average
  6. calculate the speed of the wave using wave speed = frequency x wavelength
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23
Q

what is the method for investigating waves in a solid?
(standing wave on a vibrating string) practical

A
  1. set up the apparatus to investigate wave properties of a vibrating string
  2. adjust the frequency of the signal generator until a “solid” wave is produced
  3. record the frequency shown on the signal generator
  4. use a ruler to measure wavelength, by measuring the length of 10 wavelengths and dividing by 10
    5.repeat thee procedure by adjusting the frequency until another “solid” wave is produced
  5. speed of wave can be found using equation: v =f λ
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24
Q

what is refraction?

A

the change in direction of waves caused by a change in their speed when they cross a boundary from one medium to another (at an interface)

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25
Q

how does dispersion happen?

A

refraction by a mirror

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26
Q

what happens when light enters a more dense medium (e.g air to ocean)

A

it is refracted towards the normal

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27
Q

what happens when light enters a less dense medium (e.g glass to air)

A

it is refracted away from the normal

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28
Q

what happens to waves at the boundary between two diff materials ?

A

waves can be absorbed on transmitted

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29
Q

what is the relationship between density and a wave

A

the higher the density, the slower the wave travels

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30
Q

what happens to frequency and wavelength when wave speed increases?

A

the frequency stays the same but wavelength increases

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31
Q

what are the effects of absorption, transmission and reflection?

A
  • absorption is when the material absorbs the wave so the energy from the wave is transferred to that material’s energy stores
  • transmission is where the wave enters the material but carries on travelling, so passes out the other side, leading to refraction
  • reflection is when the wave is reflected off the surface, never enters the material
32
Q

investigate the method for reflection of light by different types of surfaces and the refraction of light by different substances

A
  1. Slot the collimating slit into the ray box and turn on, producing a narrow ray of light
  2. place the first block of material on top of a piece of paper. Trace around the block using a pencil
  3. draw a normal to the block (a line at 90* to the surface of the block). Align the incident ray of light with the meeting point between the normal and the surface of the block
  4. draw the reflected ray and refracted ray. Remove the block and draw a straight line between the point of reflection and the refracted ray on the other side of the block
  5. Use a protractor to measure:
    a. the angle of incidence- the angle between the incident ray and the normal
    b. the angle of reflection- the angle between the reflected ray and the normal
    c. the angle of refraction- the angle within the material between the normal and the refracted ray
  6. repeat the experiment using a new piece of paper for each different material of block

Safety precaution:
- don’t hold the ray box as it will heat up
- take care carrying the blocks of material ( especially glass )
- the room will be darkened so that the rays are visible. take care in your surroundings

33
Q

what type of spectrum do electromagnetic waves form?

A

a continuous spectrum

34
Q

order the types of electromagnetic radiation from lowest frequency to highest frequency

A

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

35
Q

how do the speeds of EM radiation differ in a vacuum and in air?

A

all types of EM waves travel at the same velocity through a vacuum and in air

36
Q

what property of waves in diff mediums causes refraction?

A
  • velocity
  • wave speed is slower in denser materials, causing refraction
37
Q

in which direction (relative to the normal) do waves refract when entering a denser medium?

A
  • they bend towards the normal
  • the angle of refraction is less than the angle of incidence
38
Q

describe an investigation for how the amount of infrared radiation absorbed or radiated by a surface depends on the nature of that surface

A
  1. Align the infrared detector with one side of the Leslie Cube, 20cm away from the side, and take the initial temperature of the surface.
  2. Heat one side of the Leslie Cube by pouring hot water onto the surface.
  3. Measure and record the temperature of the surface every 30s for five minutes.
  4. Rotate the cube and repeat the experiment for a different surface.
  5. Plot temperature (plot on y-axis, measured in °C) against time (plot on x-axis, measured in seconds) for each different surface.
39
Q

how are radio waves produced?

A

by oscillations in electrical circuits

40
Q

how can radio waves create an alternating current in a circuit?

A

when radio waves are absorbed, they an induce oscillations in a circuit with the same frequency as the waves themselves to create an alternating current

41
Q

where do gamma rays originate from?

A

they originate from changes in the nuclei of atoms

42
Q

what health effects can ultraviolet waves cause?

A
  • they can cause the skin to age prematurely
  • they can increase the risk of developing skin cancer
43
Q

what health hazards can X-rays and gamma rays cause?

A
  • they are ionising radiation so can cause mutations in genes
  • they can lead to increased risk of developing various cancers
44
Q

what is the damage caused by gamma rays and x-rays dependant on?

A

dependant on type of radiation and dose

45
Q

give three practical uses of infrared radiation

A
  • electrical heaters
  • cooking food
  • infrared cameras
    because energy of IR is easily absorbed by the surface of objects
46
Q

give two practical uses for microwave radiation

A
  • satellite communications– > microwaves pass through the Earth’s atmosphere without being reflected or refracted
  • cooking food –> most foods contain a lot of water molecules which absorb the energy of microwaves causing temperature to increase
47
Q

give two practical uses for radio waves

A
  • television transmission
  • radio transmission
    because radio waves can travel long distances before being absorbed
48
Q

describe a practical use for visible light

A

fibre optic communication–> have short wavelength to carry a great deal of information

49
Q

describe two practical uses of ultraviolet radiation

A
  • energy efficient lamps–> short wavelength so carries more energy than visible light
  • sun tanning –> increases risk of cancer
50
Q

describe two practical uses of x-rays and gamma rays

A
  • medical imaging –> very penetrative (x-rays absorbed by bones)
  • treatments –> treating cancer
51
Q

what wave phenomenon is used by lenses to form an image?

A

refraction

52
Q

how does a convex lens form an image?

A

parallel rays of light are refracted and brought together at a point known as the principal focus

53
Q

what is meant by the focal length of a lens?

A

the distance from the lens to the principal focus

54
Q

what is the difference between the image produced by a convex and a concave lens?

A
  • convex lenses can produce real or virtual images
  • concave lenses can only produce virtual images
55
Q

what determines whether an image is diminished, inverted, real or virtual

A
  • diminished = image formed is smaller than object
  • inverted = image formed is upside down
  • real = lines join to meet a point
  • virtual = lines dont meet a point/concave lens
56
Q

why does magnification not have a unit ?

A
  • it is a ratio and so has no units
57
Q

what determines the colour of visible light waves?

A

the wavelength and frequency of the light waves

58
Q

what colour of visible light has the highest frequency?

A

blue

59
Q

what colour of visible light has the largest wavelength?

A

red

60
Q

what is meant by the term ‘specular reflection’ ?

A

reflection from a smooth surface in a single direction

61
Q

what is meant by the term ‘diffuse reflection’ ?

A

reflection from a rough surface which causes scattering

62
Q

how does a red colour filter work?

A
  • a red filter absorbs all wavelengths of light other than those in the range of the spectrum
  • this means only red light passes through the filter
63
Q

what determines the colour of an opaque object?

A
  • different objects reflect different wavelengths of light by different amounts
  • the wavelengths that are most strongly reflected determine the colour
64
Q

what happens to the wavelengths of light that aren’t reflected by an opaque object?

A

any wavelengths that aren’t reflected are absorbed by the object

65
Q

what colour does an object appear if all wavelengths are reflected by equal amounts?

A

white

66
Q

what colour does an object appear if all waves are absorbed?

A

black

67
Q

what do all bodies (objects) emit and absorb?

A

infrared radiation

68
Q

what happens to the quantity of infrared radiation emitted by an object as temperature increases?

A

the hotter the object, the more infrared radiation it will emit

69
Q

what is a perfect black body?

A

an object that absorbs all of the radiation that is incident upon it

70
Q

how much radiation does a perfect black body reflect or transmit?

A

none

71
Q

why is a perfect black body the best possible emitter of radiation?

A
  • it is a perfect absorber since it absorbs all radiation incident on it
  • a perfect absorber is also a perfect emitter
72
Q

other than intensity of radiation emitted, how does increasing the temperature of an object affect its emissions?

A

the wavelength distribution of any emission is dependant on the object’s temperature

73
Q

what can be said about the rates of emission and absorption for a body at constant temperature?

A

the body is absorbing and emitting radiation at the same rate

74
Q

what can be said about the rates of emission and absorption for a body increasing in temperature ?

A

the body is absorbing radiation faster than it is emitting it

75
Q

give an example of a body with a higher temperature than its surrounding

A

hot coffee is an object warmer than its surroundings so emits more radiation than it absorbs

76
Q

give two factors that effect the temperature of the earth

A
  1. the earth’s rate of absorption and emission of radiation
  2. the amount of reflection of radiation or radiation into space
77
Q

give an example of how a factor effects the temperature of the Earth

A

cloud cover–> cloudy nights are warmer than clear nights because clouds can reflect infrared radiation back to the earth and prevent it from being radiated into space

physics paper 2 (1 decks)

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