WAVES Flashcards

1
Q

Waves transfer ______ in the ___________ they are _______

A

waves transfer energy in the direction they are travelling

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2
Q

what is the amplitude of a wave

A

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

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3
Q

what is the wavelength of a wave

A

is the distance between the same point on two adjacent waves

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4
Q

what is the frequency of the wave

A

is the number of complete waves passing a certain per second

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5
Q

what is frequency measured in

A

hertz

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6
Q

what is the equation for the period of a wave

A

T=1/F
T= PERIOD
F=FREQUENCY

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7
Q

THE TWO TYPES OF WAVES

A

transverse and longitudinal

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8
Q

in transverse waves….

A

the oscillations are perpendicular to the direction of energy transfer

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9
Q

examples of transverse waves

A

all electromagnetic waves
waves in water
a wave on a string

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10
Q

in longitudinal waves

A

the oscillations are parallel to the direction of energy transfer

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11
Q

examples of longitudinal waves

A

sound waves

shock waves

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12
Q

equation for wave speed

A

frequency * wavelength

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13
Q

waves can be….

A

absorbed, transmitted or reflected

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14
Q

angle of incidence =

A

angle of reflection

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15
Q

what is specular reflection

A

specular reflection is when a wave is reflected in a single direction by a smooth surface

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16
Q

what is diffuse reflection

A

is when a wave is reflected by a rough surface and the reflected rays are scattered in lots of different directions

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17
Q

all EM waves are…

A

transverse waves

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18
Q

all EM waves travel…

A

at the same speed through air or a vacuum

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19
Q

WHEN a wave crosses a boundary between materials at an angle

A

it changes direction

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20
Q

what depends on how much a wave is refracted

A

how much the wave speeds up or slows down

and density

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21
Q

the higher the density

A

the slower the wave travels through the material

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22
Q

what is refraction

A

when waves change direction at a boundary

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23
Q

what happens if a wave crosses a boundary and it slows down

A

it bends towards the normal

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24
Q

what happens if a wave crosses a boundary and it speeds up

A

it will bend away from the normal

25
Q

how can you produce radio waves

A

using an alternating current in an electrical circuit

26
Q

what are radio waves used for

A

are mainly used for communication
radios
tvs

27
Q

what are microwaves used for

A

microwaves are used for communication to and from satellites
heating food

28
Q

what is infrared radiation used for

A

infrared cameras

increase or monitor temperature

29
Q

explain why signals between satellites are transmitted as microwaves

A

because they can pass through the earth atmosphere

30
Q

what is given out by all hot objects

A

infrared radiation

31
Q

uses of visible light

A

fibre optic cables to transmit data

32
Q

how do fibre optic cables work

A

they work because of reflection. the light rays are bounced back and forth until they reach the end of the fibre

33
Q

uses of UV

A

UV pens

sun tanning

34
Q

uses of xrays and gamma rays

A

they are used in medicine
xrays are used to see if people have broken bones
both used to treat people with cancer
gamma can be used as a medical tracer

35
Q

how do radiographers use xrays and gamma rays to treat people with cancer

A

these rays can kill the cancer cells

36
Q

how is gamma radiation used in a medical tracer

A

a gamma emitting source is injected into the patient and its progress is followed around the body
gamma radiation is used as can pass out of the body to be detected

37
Q

how do you get an xray image

A

xrays pass easily through flesh but not so easily through bone. the amount of radiation absorbed gives you the xray image

38
Q

what do radiographers wear to protect themselves from radiation

A

lead aprons

39
Q

what is the electromagnetic specttrum

A
radio waves
microwaves
infrared radiation
visible light 
ultraviolet
xrays 
gammarays
40
Q

as you go down the electromagnetic spectrum

A

the wavelength decreases

the frequency increases

41
Q

what are the ionising ones in the EM spectrum

A

UV
gamma
xrays

42
Q

why are low frequency waves less harmful

A

they don’t transfer much energy and so mostly pass through soft tissue without being absorbed

43
Q

why are high frequency waves dangerous

A

they all transfer lots of energy and so can cause lots of damage

44
Q

why is uv radiation dangerous

A

damage surface cells which can lead to sunburn

increased risk of skin cancer

45
Q

why are xrays and gamma rays dangerous

A

types of ionising radiation
can cause gene mutation or cell destruction
cancer

46
Q

how do lenses form images

A

by refracting light and changing its direction

47
Q

WHAt are the two main types of lens

A

concave and convex

48
Q

what is a convex lens

A

a convex lens bulges outwards it causes rays of light parallel to the axis to be brought together at the principal focus

49
Q

what is a concave lens

A

a concave lens caves inwards. It causes parallel rays of light to spread out

50
Q

what is the principal focus of a convex lens

A

is where rays hitting the lens parallel to the axis all meet

51
Q

what is the principal focus of a concave lens

A

is the point where rays hitting the lens parallel to the axis appear to come from

52
Q

to describe an image properly what do you need to say

A

how big it is compared to the object
real or virtual
upright or inverted

53
Q

how would you draw a ray diagram through a conc=vex lens

A

draw a ray from the top of the object to the lens
draw a ray from the top of the object through the middle of the lens
the ray that has touched the lens should be refracted through the focal point
the ray that goes through the middle of the lens should be extended
where the rays meet is the image

54
Q

what should you always remember when you draw rays

A

arrows on the rays

55
Q

an object at 2f will produce….

A

a real, inverted image the same size as the object and it is at 2f

56
Q

an object between f and 2f will produce…

A

a real inverted image bigger than the object and beyond 2f

57
Q

an object nearer than f will produce..

A

a virtual image the right way up bigger than the object and the same side of the lens

58
Q

concave lenses always produce a

A

virtual image

59
Q

magnification=

A

image height/object height