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physics igcse > waves- topic 3 > Flashcards

waves- topic 3 Flashcards

1
Q

waves

A

Oscillations in a medium that transfer energy not matter

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2
Q

wave motion

A

Wave motion is the transfer of energy from one point to another. We can demonstrate this by hanging an object on a stretched string and then sending a pulse down the string (by moving it up and down quickly like a wave)

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3
Q

oscillation

A

vibration repeated side to side or back and forth motion in a fixed point

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3
Q

displacement

A

distance from rest position (0 displacement)

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4
Q

amplitude (A)

A

a wave is its maximum distance from the equilibrium.
maximum displacement
from x axis to wave peak (A)

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5
Q

wavelength

A

distance between successive crests or successive troughs

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6
Q

crest (peaks) vs troughs

A

crests=The peak of a wave. The part of a wave at maximum amplitude.
troughs=The bottom of a wave. The point with minimum amplitude.

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7
Q

frequency

A

the number of waves produced each second. It is denoted by the letter f and is measured in hertz (Hz).

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8
Q

wavefront

A

an imaginary surface that we draw to represent the vibrating part of a wave

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9
Q

wave speed

A

the distance travelled by a wave each second.
frequency * wavelength

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10
Q

transverse waves

A

the particle oscillates perpendicular (at right angles) to the direction of propagation of the wave
electromagnetic radiation, water waves and
seismic S-waves
troughs and crests

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11
Q

longitudinal waves

A

the oscillation of the particles is parallel (in the same direction) to the direction of propagation of the wave
sound waves
and seismic P-waves (primary)
rarefactions and compressions

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12
Q

reflection of a wave

A

a wave ‘bounces’ off a boundary
changes direction
wave speed, frequency and wavelength does not change

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13
Q

rarefraction of a wave

A

a wave moves from one medium to another
change in speed caused by movmeent form one material to the other causes a change in wavelength, can also cause change in direction in which wave is travelling depending on angle wavefront reaches boundary
If the wavefronts are parallel to the boundary, the wave will just change speed
no change in direction

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14
Q

diffraction

A

a wave spreads as it moves through a gap. curved pattern

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15
Q

incident ray

A

The path of a wave which travels from the source. reaches boundary

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16
Q

reflected wave

A

The path of a wave which has reflected from a surface. hit boundary and bounced off

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17
Q

what happens if wavefront is parallel to surface when it hits

A

wavefront will be reflected back in the direction it came from

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18
Q

what happens when waves travel from deep to shallow if not parallel to block

A

waves slow down, due to this frequency does not change, and wavelength decreases
direction of travel will change towards the normal. angle of rarefaction is smaller than incidence wave

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19
Q

what are two ways to increase diffraction

A

decrease size of the gap
increase wavelength of wave
A gap width similar to the wavelength of the waves passing through causes a lot of spreading

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20
Q

Describe how wavelength affects diffraction at an
edge

A

this amount of diffraction increases as the wavelength of the wave increases. Waves with long wavelengths diffract more than waves with short wavelengths.

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21
Q

what diffracts more and why? sound or light waves through an edge

A

As sound waves have much longer wavelength than light waves they are much more strongly diffracted by edges. This allows sound waves to spread around corners in a way that is not possible for light.

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22
Q

describe refraction from deep water to shallow water at an angle

A

wave travelling through deep water is faster, when it enters shallow surface, it slows down and this causes a change i direciton, when waves slow down wavelengths decrease, angle of incidence is bigger than angle of rearefraction, getts smaller with bigger angle

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23
Q

what happens when a wave is travlleing from deep water to shallow water but is parallel to boundary

A

no change in direction only change in speed goes from fast to slow, wavelengths decrease

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24
Q

what is light

A

electromagnetic transverse wave

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25
Q

what is the law of reflection

A

i=r

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26
Q

what are the properties of images in a plane mirror

A

image is uprights, image is virtual, laterally inverted (right side of object is left side of image), same size, image same perpendicular distance behind mirror as object is infront

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27
Q

describe rarefraction of light

A

when light enters a different medium it changes speed and direction, same speed in same medium

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28
Q

describe rarefraction of light from a less dense medium to a more dense

A

eg. air- water or air- glass
incidence ray is bigger than refracted one refraction towards normal speed decreases, frequency is constant, wavelength decreases

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29
Q

describe rarefraction of light from a more dense medium to a less dense

A

eg. water- air or glass- air
incidence ray is smaller than refracted one, refraction away from normal, speed increases, freuqunecy is constant, wavelenth increases

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30
Q

Describe an experiment to show refraction of light by transparent blocks of different shapes

A

use a raybox to point light at an angle to a differnet medium, eg, transparnet block trace light rays by markey 3 crosses per ray and connecting with a ruler
use a protractor to measure angles
large angles have less measurment errors

or use pins by looking at their bases, and then trace their paths, repeat both expirments 5 times and calculate average refractive index (n)

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31
Q

describe refraction with ray going 90 degrees to boundary

A

no refraction

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32
Q

what are formulas for refractive indx

A

n= sini/sinr
n=1/sinc
n=v1/v2
n=wavelengthfrequnecy/ wavelength2frequency2

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33
Q

define n

A

refractive index, ratio of speeds of a wave in two different regions

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34
Q

what is meant by critical angle

A

angle of incidence that results in an angle of refraction of 90 degrees, therefore at boundary, no “seen”refraction”only reflection

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35
Q

when does total internal reflection take place

A

when light moves from more dense to less dense medium angle of incidnce= critical angle refraction= 90 degrees
angle of incidence is called critical angle

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36
Q

what are optical fibres why are they used?

A

in optical fibres only total internal reflection occurs, i is greater than critical angle used for telecommunications- carry binary digit code as a series of infrared or visible light signals , carry more info than electrical signlas and are more secure and harder to “tap”
made from glass which is much cheaper can carry several different signals down fibre at same time
used in endoscopes- bundle of optical fibre fed into patients stomach allows doctor to look inside

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37
Q

principal focus

A

he point where rays of light travelling parallel to the principal axis intersect the principal axis and converge (F)

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38
Q

focal length

A

distance between the centre of the lens and the focal point.

39
Q

principal axis

A

The horizontal line passing through the optical centre of the lens

40
Q

describe ray diagram and caracteristics of image beyond 2F

A

image is real
upside down (inverted)
smaller than object( diminuished)

41
Q

describe ray diagram and caracteristics of image at 2F

A

real
inverted
same size as object

42
Q

describe ray diagram and caracteristics of image between F and 2F

A

real
inverted
magnified

43
Q

magnificaton formula

A

image hiehgt/ object hiehgt
image distance/object distance

44
Q

describe ray diagram and caracteristics of image inbetween F and lens

A

virtual
magnified
upright
(image to the left of the object)

45
Q

describe a virtual image

A

formed when diverging rays are extrapolated backwards and does not form a visible projection on a screen

46
Q

describe how short sightedness is fixed

A

diverging lens is used
diverging lens forms a virtual image of the distance object, closer to the eye
light rays will diverge when passing through lens and form focused image on retina

47
Q

describe short sightedness

A

unfocused image formed on retina, lens is too powerful

48
Q

decribe long sightedness

A

unclear unfocussed image formed on retina, eyelens is too weak or eyeball too short

49
Q

describe correcting long sightedness

A

use convergins lens
forms a virtual image further away from object
converges light rays and a focussed image is formed on retina

50
Q

describe dispersion

A

dispersion is when white light which consists of all the colours travelling in same speed (3 *10ˆ8) hit a glass prism and because of their differnet wavelengths, travel at different speeds and undergo refraction

51
Q

what is order of colours from less refraction to more

A

red,orange, yellow, green, blue, indigo,violet

52
Q

what is meant by monochromatic

A

visible light of a single frequency

53
Q

explain red light and its refraction

A

red light has a greater speed in glass, lower freuqunecy and bigger wavelength, refracts less

54
Q

explain blue light and its refraction

A

has a smaller speed in glass, higher freuqunecy and smaller wavelength, refracts more

55
Q

what is the order of electromagnetic spectrum and trends

A

(rich men in vegas use expensive girls)
radio waves, microwaves, infrared, visible( red, violet), ultraviolet, xrays, gamma
from longest wavelength to shortest
from smaller frequency to bigger

56
Q

describe some properties of electromagnetic waves

A

all transverse waves
travel at same speed in a vaccum ( 3* 10ˆ8)
approximately same in air

57
Q

describe use of radio waves

A

radio and television
transmissions, astronomy, radio frequency
identification (RFID)

58
Q

describe use of microwavs

A

satellite television, mobile
phones (cell phones), microwave ovens

59
Q

describe use of infrared

A

electric grills, short range
communications such as remote controllers
for televisions, intruder alarms, thermal
imaging, optical fibres

60
Q

describe use of visible light

A

vision, photography, illumination

61
Q

describe use of ultraviolet

A

security marking, detecting fake
bank notes, sterilising water

62
Q

describe use of x rays

A

medical scanning, security scanners

63
Q

describe use of gamma

A

sterilising food and medical
equipment, detection of cancer and its
treatment

64
Q

describe harm of microwaves

A

internal heating of body cells

65
Q

describe harm of infrared

A

skin burns

66
Q

describe harm of ultraviolet

A

damage surface cells and eyes, skin cancer eye conditions

67
Q

describe harm of x-rays and gamma

A

cell mutation and damage to cells

68
Q

describe mobile phones and how they rely on electromagnetic radiation

A

use microwaves because microwaves cam penetrate some walls and only require short aerial for transmission and reception

69
Q

describe bluetooth and how they rely on electromagnetic radiation

A

uses radio waves because radio waves pass throguh wals but signal is weakened doing so, and with distance from device

70
Q

describe optical fibres and how they rely on electromagnetic radiation

A

uses visible light and infrared, for cable tv and high speed broadband because glass is transparent to visible light and some infrare, visible light and short wavelength infrared can carry hight rates of data

71
Q

communication with artificial
satellites

A

uses microwaves because it can pass throguh earths atmosphere and have been used to communicate to artifical satellites

72
Q

describe low orbit satellites

A

satellite phones use them, data sent very fast

73
Q

describe high orbit or geostationary setellites

A

some satellite phones and direct broadcast satellite tv, above equator

74
Q

analogue signals

A

continuoes value can be single or mixed frequency

75
Q

digital signals

A

digital can only have precise values binary digital value- 0 or 1
not continuos wave

76
Q

sound can be transmitted as

A

digital or analouge signals

77
Q

Explain the benefits of digital signaling

A

increased range due to accurate signal
regeneration- data can be sent further and have a greater range they by regenerated more accurately than analogue

send more info in shorter space of time- greater rate of transmission of data

digital signals are less affected by noise

78
Q

Describe the production of sound

A

whenever two materials rub together or a vibrating source, all longitudinal

79
Q

what is frequency in sound

A

number of oscillations of a particles on the wave per sec

80
Q

human audible frequency range

A

20- 20000 Hz

81
Q

what is needed to transmit sound

A

a medium, doenst flow/ radiate energy through a vaccum

82
Q

speed of sound in air

A

330- 350 m/s

83
Q

compression

A

a region of high particle density

84
Q

rarefraction

A

a region of low particle density

85
Q

what medium does sound waves travel the fastest and why

A

solids than in liquids and faster in liquids than in gases
because in solids particles are closer together and oscillate strong forces between molecules

86
Q

speed of sound in solid

A

5000 m/s

87
Q

speed of sound in liquid

A

1500 m/s

88
Q

Describe a method involving a measurement of
distance and time for determining the speed of
sound in air

A

use a gun and measure time taken to hear, then divide distance from person with gun to time taken to listen

89
Q

greater the amplitude (sound)

A

greater loudness of a sound

90
Q

greater freuqunecy

A

hgiher the pitch, smaller wave length, waves closer togethr

91
Q

what is an echo

A

reflection of sound waves

92
Q

formula used to calculate echos

A

2d= sound speed * time taken

93
Q

ultrasound

A

sound of frequnecy above 20KHz

94
Q

what are uses of ultrasound in nondestructive testing of materials

A

ultrasound sent through metal or plastic or other materials, crack will reflect ultrasound eave, good matrial will not reflect, material is tested without cutting it open

95
Q

what are uses of ultrasound in medical scanning of soft tissue

A

ultrasound reflects off human tissue of differnet densities, doctor uses transmitter to send ultrasound which reflects off tissue and tected by receiver, comp can calculate depth of tissue
eg. imaging fetus
safe and non ionising
ultrasound travels at differnet speeds in different types of tissue, greater the density of tissue grater speed, faster in muscle slower in fat

physics igcse (8 decks)

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