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Physics (old) > waves ~~~~~~~~~~~~ > Flashcards

waves ~~~~~~~~~~~~ Flashcards

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1
Q

what are progressive waves?

A

an oscillation that travels through matter (or in some cases vacums) that transfer energy from one place to another without transferring matter

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2
Q

what is a longitudinal wave?

A

direction of energy transfer is parallel to oscillations

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3
Q

what are transverse waves?

A

direction of energy transfer is perpendicular to oscillation

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4
Q

what is the wave equation?

A
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5
Q

what can be measured from distance displacement wave profiles?

A
  • wavelength
  • amplitude

snapshot of the wave

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6
Q

what would a displacement distance wave profile look like for a transverse wave?

A
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7
Q

what would a displacemnet distnace wave profile look like for a longitudinal wave?

how would you identify compressions and rarefactions?

A

centre of compression/ rarefaction has 0 displacement
* centre of compression: positive –> negative
* centre of rarefaction: negative–> positive

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8
Q

How do you convert between radian and degrees?

A

360°= 2π radian
180°= π radian

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9
Q

what is “phase difference”?

A

difference in displacement of particles along a eave, or in 2 different waves

measured in difference

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10
Q

what is meant by the term “in phase”?

A

phase difference of 0 or a multiple of 2π radians (360°)

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11
Q

what is meant by the term “antiphase”?

A

a phase difference of π radians (180°)

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12
Q

what can be measured from a distplacment time wave profile?

A
  • amplitude
  • time period (frequency)
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13
Q

what is reflection?

A

when a wave changes direction at a boundary between two media, remaining in the original medium
* wavelength, frequnecy do not change

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14
Q

what is a wavefront?

A

Lines of constant phase

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15
Q

what is refracation?

A

when a wave changes speed as it changes direction at the boundary of two media
* frequnecy the same
* wavespeed and wavelength change

will always be partial reflection

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16
Q

what happens when waves moves to denser mediums

A
  • normal waves: speed up, move away from the normal
  • EM waves slow down, move towards the normal
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17
Q

what is diffraction?

A

the spreading out of a wave front as it passes through a gap
* hyeogens principle: when a wave is disturbed each point where there is a disturbance becomes a source for a spherical wave

maximim difraction when gap is same size as incident wavelength

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18
Q

define displacement

A
  • distance and direction moved from the equilibrium position
  • [s]
  • units SI (m)

vector so negative or positive

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19
Q

define Amplitude

A
  • the maximum displacement from the equilibrium position
  • [A]
  • units SI (m)

vectors positive or negative

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20
Q

define Wavelength

A
  • the distance between two adjacent vibrating particles/points with same velocity, at same displacement
  • [λ]
  • units SI (m)
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21
Q

define Time period

A
  • the time taken for one oscillation/ wave to move one whole wavelength past a given point
  • [T]
  • units SI (s)
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22
Q

define frequency

A
  • the number of wavelengths passing a given point per second
  • [f]
  • units SI (Hz)
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23
Q

define Wave Speed

A
  • the distance travelled by the wave per unit of time
  • [v]/[c]
  • SI unit ms-1
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24
Q

describe distance displacment graphs

A
  • shows the displacement of several points on a wave at a particular time
  • “snapshot”
  • wavelength, amplitude

several particles

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25
Q

describe displacemnt time graph

A
  • shows the displacment of a point at several times
  • “video of a single particle”

time period, frequnecy,amplitude

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26
Q

Clock and sin wave

A
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27
Q

Clock and sin wave

A
28
Q

Are these waves inphase, out of phase or Antiphase

A

In phase as everything is perfectly aligned

29
Q

How would you calculate if waves are in phase or anti phase according to wavelength ?

A
30
Q

How would you calculate if 2 waves are in phase or anti phase according to phase difference?

A
31
Q

Define electro magnetic waves

A

Waves that travel by oscillations of the electromagnetic field. Always transverse waves

32
Q

What is the electro magnetic spectrum and the corresponding wavelengths ?

A
33
Q

What is the order of visible light

A

ROYGBIV
Richard of York gave battle in vain
Red, orange, yellow, green, blue, indigo, violet

34
Q

What is polarisation ?

A

Can only be done to transverse waves, applying a filter to light

35
Q

What is a plane polarised light?

A

A transverse wave where oscillations are limited to only one plane

36
Q

What happens when two polarised filters are perfectly aligned ?

A
37
Q

What happens when two Polaroid filters are at 90° to each other?

A
38
Q

Describe the use of Polaroid sun glasses

A
  1. light is horizontally polarsied (from water/metal surfaces)
  2. sunglasses have vertically alligned filtesr blobking all this polarised light
  3. this reduces the bright glare
39
Q

What is Snells Law?

A
40
Q

What is refractive index?

A

How much it slows down

41
Q

What happens to the angle of incidence / refraction when moving from one medium to another?

A
42
Q

Define total internal reflection

A

The reflection of all light back into the original medium when hitting a boundary between two media;
* the original medium will have a higher refractive index (n1>n2)
* the incidence angle at the boundary must be greater than the critical angle

43
Q

Define critical angle

A

The angle of incidence at the boundary between 2 media, that will produce an angle of refraction of 90°

44
Q

What is the critical angle ?

A
45
Q

What is the formula for the critical angle?

A
46
Q

What happens in fibre optic cables ?

A

Total internal reflection

47
Q

Does frequency change when wave speed changed ?

A
48
Q

Does refractive index vary with frequency?

A
49
Q

What are the two types of waves and how do they specifically transfer energy?

A

Waves transfer energy via oscillations

50
Q

what is the phase of a point/particle?

A

the fraction of a complet cycle/ wave that a point is at

51
Q
A
52
Q

What happens to the wavefronts in diffraction?

A
53
Q

Describe refraction in terms of wavefronts

A

Part of wavefronts change speed first causing the change in direction, when at an angle to the normal

54
Q

What are the refraction rules for EM waves and mechanical waves?

A
55
Q

what are the rules for diffraction?

A
  • wave speed, wavelength: do not change
  • the longer the wavelength the more the wave spreads out
  • the smaler the gap relative to the wavelength, the greater the diffraction
56
Q

what is polarisation?

A
  • a property of transverse waves
  • defines the plane of oscillation of the wave
57
Q

what is the plane of polarisation of an EM wave?

A

the plane in which the electric field vibrates

58
Q

how is light (EM waves) polarised with filters?

A
  • plane of allignment of the filter is the plane in which E-field oscillations pass through
  • transmitted light is polarised in the same plane

allows all components of waves in that certain direction not just E fiel

59
Q

what is unpolarised light?

A
  • **wave trains **(a group of waves of equal or similar wavelengths travelling in the same direction)
60
Q

What is Malus Law?

A
61
Q

how is light polarised by reflection?

A
  • on metal surfaces and water
  • polarised in the horizontal plane
62
Q

How do polarising filters work?

A
63
Q
A
  • unpolarised light from lamp
  • p1 polarises the light in the vertical plane
  • p2 polarises light int the horizontal plane
  • but there is no component of vertically plane polarised light that lays in the horizontal direction
64
Q
A
65
Q
A

Physics (old) (10 decks)

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