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Physics A Levels Unit 2 Re-run > 5. Wave properties > Flashcards

5. Wave properties Flashcards

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1
Q

What is the principle of superposition?

A

When 2/more waves (of the same type) occupy the same position in space then the resultant wave is found by the vector sum of the individual displacements of the waves at any point

When two or more waves cross at a point, the displacement at that point is equal to the sum of the displacements of the individual waves

Gl o7

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2
Q

Define constructive interference?

A
  • Same type of wave (transverse)
  • Waves are in-phase
  • Waves reinforce each other to produce a larger wave
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3
Q

Define destructive interference?

A
  • Same type of wave (transverse)
  • Waves are anti-phase
  • Waves cancel each other to produce a smaller wave
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4
Q

Define total destructive interference?

A

Produces a zero resultant wave known as cancellation

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5
Q

Should be easy to know how to draw resultant wave forms with principle of superposition

A

I believe

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6
Q

How is a stationary wave formed?

A

Interference of:
- Two progressive waves
- Of same frequency & amplitude
- Travelling in opposite directions

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7
Q

Alternate name for stationary waves?

A

Standing waves

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8
Q

How are stationary waves commonly set up?

A
  • Wave reflecting back from a surface
  • Reflected waves interfere with original wave
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9
Q

Explain stationary waves?

A
  • Incident wave & reflected wave
  • Interfere each other
  • Superposition happens
  • Only certain frequencies to result resonance condition
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10
Q

Explain nodes

A

Places along wave w/ zero displacement
Destructive interference

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11
Q

Explain antinodes

A

Places between nodes that oscillate & suffer maximum displacement

  • range of (maximum) constructive and destructive interference occur here
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12
Q

Formula for distance between adjacent nodes/adjacent antinodes?

A

Inter-nodal spacing is λ/2

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13
Q

State the amplitude for a stationary wave?

A

Varies between 0 and 2A

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14
Q

State the amplitude for a progressive wave?

A

A for all particles as the wave travels

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15
Q

State the frequency for a stationary wave?

A

Same for all particles except at nodes

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16
Q

State the frequency for a progressive wave?

A

Same for all particles

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17
Q

State the energy for a stationary wave?

A

No transfer
(energy stored within each loop)

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18
Q

State the energy for a progressive wave?

A

Energy transfer

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19
Q

State the waveform for a stationary wave?

A

Does not advance

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20
Q

State the waveform for a progressive wave?

A

Advances at the speed of wave

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21
Q

State the phase for a stationary wave?

A

All particles vibrate in-phase within a loop
(adjacent loops in antiphase)

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22
Q

State the phase for a progressive wave?

A
  • Over one wavelength
  • Particles have a range of phases between 0 and 2π
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23
Q

Explain standing waves in a string?

A

String can be vibrated to form a stationary wave with both ends fixed

Both ends form nodes

24
Q

Explain standing waves in a closed pipe?

A

Vibrating column of air with one end closed and the other open

One one forms a none the other an antinode

25
Q

Explain standing waves in an open pipe?

A

Vibrating column of air with bond ends open

Both ends form antinodes

26
Q

State the formula of wavelength for their first harmonic within string and open pipe standing waves

A

λ = 2l

27
Q

State the formula of wavelength for their first harmonic within closed pipe standing waves

A

λ = 4l

28
Q

Formula for when u increase harmonic of string and open pipe standing waves?

A

2nd - λ2 = l
3rd - λ3 = 2l/3
4th - λ4 = l/2
5th - λ5 = 2l/5

I could or may seem to understand the pattern

29
Q

Formula for when u increase harmonic of closed pipe standing waves?

A

2nd - impossible
3rd - λ3 = 4l/3
4th - impossible
5th - λ5 = 4l/5

The trick is every odd n°
In addition, this the only different between the other 2

30
Q

State 5 stationary wave experiments

A
  1. Stationary waves on a string/wire
  2. Stationary mechanical waves on a wire loop
  3. Stationary Em waves using microwaves
  4. Stationary sound waves in closed pipes
  5. Measuring the speed of sound using a closed tube
31
Q

U may add cards related to the 5 other experiments somehow

A

Hm

32
Q

What is diffraction of a wave?

A

The spreading out of a wave’s energy around obstacles and through gaps

33
Q

For a diffraction thru gap, what happens when gap width decreases?

A

If gap width decreases, amount of diffraction (angle of spread) increases

34
Q

When does maximum diffraction occur?

A

Gap width equal/slightly smaller than λ

35
Q

When is the diffraction effect at its greatest?

A

Wavelength is equal to/slightly greater than the obstacle or the gap width

36
Q

Explain coherent sources during 2 source interference

A
  • Coherent when they produces waves of same freq
  • Same amplitude and maintain constant phase difference
37
Q

2 examples of coherent wave source?

A
  • Laser
  • Single slit aperture
38
Q

Explain incoherent wave sources during 2 source interference

A
  • 2 sources of waves having different frequencies
    -Will have phases constantly changing
  • Therefore pattern produces constantly changing
39
Q

2 examples of incoherent wave sources?

A
  • Sunlight
  • Light bulbs
40
Q

Formula for interference fringe separation formula?

(in data booklet)

A

λ = (a△y)/D

41
Q

Explain each symbol within interference fringe separation formula
(all must be in m units)

λ = (a△y)/D

A

λ - wavelength (m)
a - source separation (m)
D - distance from source (m)
△y - fringe separation (m)

42
Q

What is path difference?

A
  • The difference in distance that two waves must travel
  • From their sources to a given point
43
Q

Explain how an interference pattern is formed?

A

If the light from two point sources overlaps, the interference pattern maps out the way in which the phase difference between the two waves varies in space

Probably can’t learn in time

44
Q

How is a double slit experiment set up?

A

Need:
- Monochromatic light source
- Single slit
allowed for single wave from to reach double slits
- Double slits
All wave fronts gon’ be in phase,
Thus shall emit coherent waves

45
Q

What is meant by monochromatic light?

A

single-wavelength light

46
Q

In a double slit experiment, explain the bright fringes seen

A
  • Constructive intereference
  • Between 2 beams coming from both slits
  • Must be arriving in-phase
47
Q

In a double slit experiment, explain the dark fringes seen

A
  • Destructive interference
  • Between 2 beams coming from both slits
  • Must be arriving out-of-phase
48
Q

How to make double slit method more accurate?

A

Add more slits….

49
Q

What is diffraction grating?

A

Consisting of many narrow, parallel and equally spaced slits that transmit light

50
Q

3 advantages of using diffraction grating?

A
  1. More light can pass thru = fringes r brighter
  2. Fringes more well-defined, better cancellation either side of centre of fringe
  3. Fringes more spread out due to much smaller slit separation
51
Q

What is the formula for diffraction grating?
(it’s in data booklet, tho reversed)

A

nλ = dsinθ

52
Q

Explain each symbol within formula of diffraction grating
(units gotta be m mostly)

nλ = dsinθ

A

n - order number
λ - wavelength (m)
d - slit separation (m)
θ - angular position of order from centre (degrees)

53
Q

How do u derive for nλ = dsinθ?

A

First, look between 2 slits and make some right angled triangle?
Honestly, better if u had a picture, too bad u can’t place any
1. AC is the path difference between the adjacent waves
2. For 2 adjacent waves the path difference AC = dsinθ
3. At a bright maxima the waves are in-phase
4. Therefore, AC = nθ
5. Equating gives: nλ = dsinθ

54
Q

Describe the appearance of the diffraction pattern from white light incident upon a diffraction grating

A

The central maxima is narrow and white. The surrounding maxima are split into the colours red - violet. The fringes get broader with each other. Eventually the colours overlap.

55
Q

Hope for the best

A

Physics A Levels Unit 2 Re-run (11 decks)

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