12 - Waves 2 Flashcards

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1
Q

What is the principle of superposition?

A

When two waves meet at a point, the resultant displacement at that point is equal to the sum of the displacements of the individual waves.

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2
Q

What is superposition?

A

When waves overlap and produce a wave with a different displacement.

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3
Q

What is interference?

A

When two progressive waves continuously pass through each other and superpose, producing a resultant wave.

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4
Q

What is constructive interference?

A

When two waves that are in phase superpose, the resultant displacement will be greater than the displacement of each wave.

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5
Q

What happens to intensity when you increase amplitude?

A

It increases

Intensity =k(amplitude^2

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6
Q

What is destructive interference?

A

When two waves that are in antiphase superpose, the resultant displacement is lower than the displacement of each wave.

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7
Q

What happens when two waves with the same amplitude meet in antiphase?

A

The resultant wave has an amplitude of 0.

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8
Q

If two sound waves superposed in phase, what would happen to the sound?

A

It would get louder.

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9
Q

What is an interference pattern?

A

When two waves spread out and superpose at different points, producing a pattern of minima and maxima.

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10
Q

What is required for a stable interference pattern?

A

The waves must be coherent.

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11
Q

What is coherence?

A

The two waves must have a constant phase difference.

The same frequency and wavelength.

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12
Q

What is a maxima?

A

Constructive interference.

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13
Q

What is a minima?

A

Destructive interference.

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14
Q

What is path difference?

A

The difference in the distance that two waves have traveled from their sources.

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15
Q

What is path difference measured in?

A

Metres

Often in n(wavelengths) — wavelength is measured in metres

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16
Q

Describe the path difference that will cause two waves to meet at a point in phase.

A

A whole number of wavelengths.

0,1,2,3…

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17
Q

Describe the path difference that will cause two waves to meet at a point in antiphase.

A

A half number of wavelengths.

1/2 3/2 5/2 7/2 …

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18
Q

Describe the point where two waves would meet if their path difference was 100 wavelengths.

A

Maxima

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19
Q

Describe the point that two waves would meet at if their path difference was 50.5 wavelengths.

A

Minima

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20
Q

What is the central maxima?

A

A maxima where the path difference is 0.

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21
Q

What is the first order minima?

A

A minima where the path difference is 1/2 wavelengths.

22
Q

What is the first order maxima?

A

A maxima where the path difference is 1 wavelength.

23
Q

Describe the path difference of the 3rd order minima.

A

5/2 wavelengths.

24
Q

What is the PHASE DIFFERENCE of the first order maxima?

A

360 degrees / 2 pi

25
Q

What is the phase difference for any minima?

A

An odd number of pi radians.

1,3,5…

180,540,900

26
Q

What is the phase difference of any maxima?

A

An even number of pi radians.

0,2,4,6…

0,360,720,1080

27
Q

What does monochromatic light mean?

A

It is all the same colour and therefore all the same frequency.

28
Q

How can you produce monochromatic light?

A

With a colour filter.

29
Q

What does the positioning of the slits in Young’s Double Slit experiment achieve and how?

A

Light goes through a single slit and then diffracts.

Arrives at the double slits in phase and then diffracts again.

This ensures that the waves are coherent.

Light is monochromatic so all the same frequency.

30
Q

What does the Young Double Slit experiment produce on the screen?

A

An interference pattern of alternating bright and dark fringes.

31
Q

What is a maxima / maxima of visible light interference called?

A

Bright fringe / dark fringe

32
Q

What is the equation used to calculate the wavelength of a wave in the double slit experiment (or similar -> two coherent sources)

A

wavelength = (distance between slits * distance between fringes) / distance from slits to screen

ax/D

33
Q

When does the equation for the young double slit experiment only apply?

A

if a &laquo_space;D

If the distance between the slits is much less than the distance between the slits and the screen.

34
Q

How are stationary waves formed?

A

When two progressive waves with the same frequency (and sometimes amplitude) travelling in opposite directions are superposed.

35
Q

What is a node?

A

A point in a stationary wave where the displacements of the two progressive waves cancel out as they are in antiphase.

36
Q

What is an antinode?

A

A point in a stationary wave where the displacements of the two progressive waves are at their maximum / minimum and the displacement is at its maximum as they are in phase.

37
Q

Is energy transferred in a stationary wave?

A

NO

38
Q

What happens to energy in a stationary wave?

A

It is trapped at the antinodes, going from elastic potential to kinetic and vice versa.

39
Q

Describe the oscillation at a node.

A

None

40
Q

Describe the oscillation at an antinode.

A

Maximum

41
Q

What is the fundamental frequency of a string?

A

The minimum frequency of a stationary wave of a string.

42
Q

What does the fundamental frequency of a string depend on?

A

The string’s mass, tension and length.

43
Q

What do the two ends of a string have to be when a stationary wave is formed?

A

Nodes.

44
Q

What are harmonics?

A

Integer multiples of the fundamental frequency.

Higher frequencies of stationary waves.

45
Q

What type of waves can stationary waves be formed in?

A

Longitudinal and transverse.

46
Q

How are stationary sound waves formed?

A

When sound waves reflect off of a surface.

47
Q

How can stationary waves be formed in tubes?

A

When the air column in the tube is made to vibrate at the fundamental frequency.

48
Q

What is the fundamental frequency of and air column in a tube related to?

A

The length of the tube.

49
Q

Describe what must be at the ends of a tube which is closed at one end when a stationary wave is formed.

A

A node at the closed end and an antinode at the open end.

50
Q

Describe what must be at both ends of a tube which is open at both ends when a stationary wave is formed.

A

Antinodes.

51
Q

Describe the integer multiples of the fundamental frequency for a tube that is closed at one end.

A

They are always odd multiples.

52
Q

Describe the integer multiples if the fundamental frequency for a tube that is open at both ends.

A

They can be any integer.