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physics > waves > Flashcards

waves Flashcards

1
Q

what do waves transfer

A

energy

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2
Q

what do mechanical waves travel through

A

a medium (matter)

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3
Q

whatre all waves categorised into

A

transverse or longitudinal

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4
Q

describe an give an example for transferse waves

A

they osciate perpendiculat to the direction of energy transfer. electromagnetic waves

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5
Q

describe and give an example of longitudinal waves

A

they osscilate parallel to the direction of energy transfer, sound and water waves

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6
Q

whats the equation to calculate wave speed

A

wavespeed=frequency x wavelength

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7
Q

whatre compressions and rarefactions

A

in longitudinal waves
-compression is when the waves are close together
-rarefaction is when theyre spread lut

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8
Q

what happens to waves at a boundary between 2 different matierials

A

theyre either
-reflected
-transmitted
-absorbed

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9
Q

whats refraction

A

when waves change direction as they cross from 1 medium to another due to a change in velocity

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10
Q

incident ray and incident angle =..

A

reflected ray and reflected angle

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11
Q

whatre the 5 different ways to descrube wave motion

A

-frequency in Hz
-wavelentj
-period (1/f)
-amplitude
-wavefront

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12
Q

whatre electromegnetic waves

A

transferve waves that tranfer energy from the source of thw wave to an absorber

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13
Q

whats the wavespeed of all transferve waves

A

300 million m/s

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14
Q

name all the waves in the electromegnetic spectrum

A

RAW MEAT IS VERY UNSANITARY EXCEPT GIRRAFES
-radio waves
-microwaves
-visible light
-ultraviolet
-xrays
-gamma rays

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15
Q

what happens as you go across the spectrum

A

-wavelength decreases ans frequency increases

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16
Q

whats meant by diffraction

A

the spreading out of waves as they apass through a gap or obsticle

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17
Q

what happens to diffraction when the gap is narrow

A

the waves spread further away from the gap

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18
Q

how do we see different visible light

A

its detected by our eyes in terms of wavelength

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19
Q

all objects —- and —– infrared radiation

A

emmit and absorb

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20
Q

what does the frequency and amount of emitted radiation depend on

A

the temp and surface of a given object
-hotter -> more radiaton emitted

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21
Q

what 4 waves are used for communication

A

-microwaves
-radiowaves
-infrared
-visible light

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22
Q

whats an optical fiber

A

thin and transparent fibers that transfer signals by either visible light or infrared radiation

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23
Q

why are shorter radiowaves more useful in communications

A

because they can carry more info without a weakend signal and theyre more easily absorbed

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24
Q

whatre the uses of radiowaves

A

-tv systems
-radio systems
-bluetooth

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25
Q

whatre the uses of microwaevs

A
  • mobile phones
    -satalites
    -microwave ovens (when waves are absorbed by water molecules)
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26
Q

whatre the uses of infrared rays

A
  • tv remote controls
    -night vision devices
    -heating
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27
Q

whatre the uses of visible light

A

-optic fiber communications, photography

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28
Q

whatre ultraviolet rays used for and whyre they harmful

A
  • security marking and sun beds
    -can cause skin cancer and blindness
29
Q

whatre the issues with x rays gamma rays

A

are ionising
-x rays can kill cells and gamma rays can cause genetic mutations

30
Q

whatre the properties of x rays

A

-affect photographic films in the same ways as light
-absorbed by metal and bones (dense)
-stopped by lead
-transmitted by healthy tissues

31
Q

whatre the adv and disadvantages of ct scans

A
  • adv: produce detailed 3d images differentiate between soft and hard tissue
    dis- expensive and give higher radiation doses
32
Q

whatre the uses of gamma rays and what are the effects of large doses

A
  • used to steralise medical equipment , kill harmful bacteria in food and kill cancer cells
    -can cause genetic mutations in large dosages
33
Q

what type of waves are sound waves

A

longitudinal waves that travel through a medium

34
Q

whats the frequency range of the human ear

A

20hz to 20,000 hz

35
Q

how are echos created

A

by soundwaves being reflected by a smooth and hard surface

36
Q

how are sound waves defracted

A

when they pass through a gap (ex-door)

37
Q

what happens when the frequency of a sound wave increses

A

the pitch increases

38
Q

what happens when the amplitude of a sound wave increases

A

the sound becomes louder

39
Q

whys ultrasound scans (prenatal) safer than xrays

A

theyre nonionising and usually reflected

40
Q

whatre ultrasound waves

A

sound energy with a frequency above human hearing (over 20,000 hz)

41
Q

how can u calculate the distance between different mediums

A

distance = wavespeed x time

42
Q

whatre the uses of ultrasound waves

A

ultrasound scans in medicine (prenatal scans)
destroying kidney stones

43
Q

whats a plane mirror

A

a perfectly flat mirror

44
Q

whats the law of reflection

A

in a plane mirror, angle of incidence is equal to the angle of reflection

45
Q

whatre angles of incidence,reflection and refraction always measured between

A

the ray and the normal

46
Q

whatre the features of.a virtual image

A

virtual and upsright,cant be projected onto a screen

47
Q

why can real images be shown on a screen

A

because all the different light rays are fo used directly onto the screen

48
Q

whats meant by the refraction of light

A

the change in direction of light rays when traveling across a boundary from 1 medium to another

49
Q

what happens when light rays travel from air to glass

A

the incident ray anglr is greater than the reflected ray angle and light rays bend towards the normal

50
Q

what happens when light rays travel from glass to air (less dense medium)

A

reflected angle is greater than the incident angle and the light ray is reflected away from the normal

51
Q

whats the 1 case wwhere the velocity of wave doesnt change when entering a difff medium

A

if it enters at 90 degrees (along the normal)

52
Q

what happens when light is refracted by a prism

A

a dispersion of light waves and the formation of a spectrum

53
Q

whats the refractive index

A

in terms of wavspeed, speed of light in vaccum/speed of light in medium

54
Q

what does the refractive index measure

A

how much a medium can reflect a light ray

55
Q

whats the law of reflection

A

n(refractive index) = sin i(incident angke)/sin r (refracted angle)

56
Q

whats the relationship between the refractive index and the critical angle

A

n= 1/sinc

57
Q

whats total internal reflection and when can it occur

A

in a dense to less dense medium.
if angle of incidence is greater than the critical angle.

58
Q

what type of images do convex lenses produce

A

real image (lines meet)

59
Q

how do you describe an image

A
  • upright or inverted
    -real or virtual
    -magnified or dimminished
60
Q

what type of image does concave lenses form

A

virtual

61
Q

how do you calculate magnification size

A

image height/object hieght

62
Q

whats the job of the retina

A

to focus images

63
Q

whats the job of the cillary muscles

A

they alter thickness of an eye lens and are attached by the suspensory ligaments

64
Q

what 2 strcutures refract light entering the cornea

A

cornea and lens

64
Q

whats the near point of the human eye

A

25 cm

64
Q

what lenses are used to correct short signtedness

A

concave (diverging)

65
Q

whar lenses are used to correct long signtedness

A

convex (converging lenses)

66
Q

how are lases used

A

in eye surgery to correct visual defects

67
Q

whats the equivilant of film in cameras

A

the retina in the eye

physics (10 decks)

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