Superposition and interference

Question 1

What is superposition?

Answer 1

when two or more waves pass through each other and combine according to the principle of superposition. it is the vector sum of the displacements of the waves passing through each other

Question 2

principle of superposition?

Answer 2

the resultant displacement at a point is equal to the vector sum of individual displacements at that point

Question 3

What is the effect of superposition?

Answer 3

interference

Question 4

Superposition can only happen to ….

Answer 4

waves of the same type

Question 5

What does it mean if two waves are in phase?

Answer 5

two waves are at the same point in the wave cycle. These will produce constructive interference

Question 6

What does it mean if two waves are out of phase

Answer 6

two waves are in exactly oppsosite points in the wave cycle

these will produce destructive interference when they superpose

Question 7

What is a real life application of destructive interference

Answer 7

noise cancelling in e.g. aeroplane

Question 8

What is the path difference of constructive interference/

Answer 8

full wavelengths

n(lamdba)

Question 9

What is the path difference of destructive interference

Answer 9

half wavelength

n + 1/2

Question 10

What is the phase difference?

Answer 10

how much one wave lags behind the other in degrees or radians
a path difference is in terms of wavelengths

Question 11

Can interference happen when observing superposition of waves of different wavelengths and frequencies

Answer 11

Yes, but it happens in a jumble

Question 12

What do the sources have to be to get interference patterns?

Answer 12

coherent

Question 13

What does it mean when we have coherent sources?

Answer 13

have the same wavelength, frequency and a fixed phase difference

Question 14

When does stable interference occur?

Answer 14

• waves are of the same type
• sources are coherent
• similar displacement at point of superposition

Question 15

What is the amplitude when destructive interference happens?

Answer 15

0

Question 16

Does interference occur in all types of waves, either it is longitudinal or transverse?

Answer 16

yes

Question 17

How can we observe interference patterns?

Answer 17

• using a ripple tank
• slits
• double slit
• diffraction grating

Question 18

How can we produce coherent light sources?

Answer 18

by passing a single wavelength of light (which can be achieved using a singular slit) through a double slit

Question 19

equation to remember?

Answer 19

lambda = Sx / D 
where 
lambda = wavelength 
s = slit width 
x = fringe seperation 
D = distance from slits to eyepiece

Question 20

light of a one single wavelength is called

Answer 20

monochromatic light - essentially 1 colour

Question 21

What is the name of the light which is a mixed of colours?

Answer 21

white light