Interference and Diffraction

Question 1

The principle of superposition

Answer 1

The resultant displacement at any point is found by adding the displacements of each separate wave

Question 2

What is the adding together of waves called

Answer 2

Interference

Question 3

When it makes a bigger waves it’s ______ interference

Answer 3

Constructive

Question 4

When it makes no wave it’s ______ interference

Answer 4

Destructive

Question 5

What happens to the waves when they are antiphase

Answer 5

They cancel out

Question 6

Path difference of λ =

Answer 6

Phase difference of 2λ radians

Question 7

Difference between nodes =

Answer 7

Difference between anti-nodes = 1/2 λ

Question 8

How does interference work with reflected waves

Answer 8

The transmitter releases two waves and one of those two is reflected to form a triangle. The wave reflected must travel the (distance x λ) so that the waves are both received in phase.

Question 9

If the path difference is whole then the interference is

Answer 9

Constructive

Question 10

If the path difference has an extra half wavelength then the interference is

Answer 10

Destructive

Question 11

Stationary wave definition

Answer 11

A wave meets and identical wave moving in the opposite direction at the same speed, frequency and amplitude at superposition

Question 12

Nodes definition

Answer 12

The waves cancel out so that there’s no oscillation

Question 13

Antinodes definition

Answer 13

Maximum oscillation

Question 14

Progressive waves characteristics

Answer 14

• Transfer energy
• Vibrate at same amplitude
• Oscillate over the same path but with a phase lag

Question 15

Stationary waves characteristics

Answer 15

• Stores energy
• Varies from 0 to max
• Between 2 nodes all particles oscillate in phase on either side of the node they are antiphase

Question 16

1st harmonic of a closed wave wavelength

Answer 16

2L

Question 17

2nd harmonic of a closed wave wavelength

Answer 17

L

Question 18

3rd harmonic of a closed wave wavelength

Answer 18

2L/3

Question 19

4th harmonic of a closed wave wavelength

Answer 19

1/2L

Question 20

Tension equation in symbols

Answer 20

c = √T / μ

Question 21

Tension equation in words

Answer 21

Speed = the square root of ( tension / mass per unit length )

Question 22

Closed pipe characteristics

Answer 22

Closed at one end, where the node is n and open at one end, where the anti node is

Question 23

Is it possible to get even quarters of wavelength for a closed pipe

Answer 23

No

Question 24

1/4 wave of a closed pipes wavelength

Answer 24

4L

Question 25

3/4 wave of a closed pipes wavelength

Answer 25

4L/3

Question 26

5/4 wave of a closed pipes wavelength

Answer 26

4L/5

Question 27

Open pipe characteristics

Answer 27

Open at both ends where the antinodes are

Question 28

Is it possible to get odd 1/4 of waves of an open pipe

Answer 28

No

Question 29

1/2 wave of a open pipes wavelength

Answer 29

2L

Question 30

1 wave of a open pipes wavelength

Answer 30

2L/2

Question 31

3/2 wave of a open pipes wavelength

Answer 31

2L/3

Question 32

Diffraction definition

Answer 32

The bending of waves when they pass through a gap or curves round edges

Question 33

Diffraction definition

Answer 33

The bending of waves when they pass through a gap or curves round edges

Question 34

What affects diffraction

Answer 34

It depends on the wavelength and the gap it passes through

Question 35

The bigger the gap to the wavelength, there is ______ diffraction

Answer 35

Little

Question 36

What happens when waves pass through a gap that is similar size to their wavelength

Answer 36

Lots of diffraction

Question 37

Why is light hard to diffract

Answer 37

The wavelength is very small

Question 38

What’s the name of the centre line in a diffraction pattern

Answer 38

Central maximum

Question 39

What’s the name of the light up lines in a diffraction pattern

Answer 39

Subsidiary maxima

Question 40

What’s the name of the dark line in a diffraction pattern

Answer 40

Minimum

Question 41

What interference is subsidiary maxima

Answer 41

Constructive

Question 42

What interference is the minimum

Answer 42

Destructive

Question 43

What is the diffraction angle

Answer 43

The angle between the central maximum and the 1st minimum

Question 44

How to calculate the diffraction angle in words

Answer 44

Sine of angle of first minimum = wavelength of waves / width of gap

Question 45

How to calculate the diffraction angle in symbols

Answer 45

Sin0 = λ / b

Question 46

What does a ripple tank show

Answer 46

Interference pattern

Question 47

Crest of a wave

Answer 47

The highest point of a wave

Question 48

Trough of a wave

Answer 48

The lowest point of a wave

Question 49

For a steady interference we need….

Answer 49

Coherent wave sources and are always in phase

Question 50

Fringe spacing definition

Answer 50

The space between 2 minimums

Question 51

Fringe spacing symbol

Answer 51

w

Question 52

What condition is needed for Youngs equation

Answer 52

Split spacing is much smaller than distance between slits and screen

Question 53

Youngs equation in words

Answer 53

Wavelength of light / separation of 2 splits = fringe spacing / distance between slit and screen

Question 54

Youngs equation in symbols

Answer 54

λ / s = w / D

Question 55

Difference between Youngs double slit experiment and a diffraction grating

Answer 55

A diffraction grating forms much brighter maximas as there are way more splits and they are also sharper as superposition occurs in precise directions

Question 56

Which is more accurate Youngs double slit experiment or a diffraction grating

Answer 56

A diffraction grating

Question 57

Diffraction grating equation in words

Answer 57

The order of maximum x wavelength = grating spacing x sine of angle centre to maximum

Question 58

Diffraction grating equation in symbols

Answer 58

nλ = dsin0

Question 59

How to work out grating space

Answer 59

1 / number of lines per mm