Superposition phase difference and interference

Question 1

What is superposition ?

Answer 1

When two waves interact, the resultant displacement is the vector sum of the individual displacements

Question 2

What is phase difference and what is the equation for phase difference ?

Answer 2

How far out of sync the two points are on a wave (or two waves)
x/lamda *360

Question 3

What is coherence ?

Answer 3

Two waves are coherent when they have a constant phase difference

Question 4

Explain the double slit experiment

Answer 4

There are two slits (openings) which waves emerge (they are coherent)
At slit one the wave reaches point p at maximum and the same at slit two
This means we will get constructive interference at point p
Then at point p we will have a very bright spot
This is because at point p the two waves meet peak to peak and they would add up

Question 5

What are the conditions for constructive interference ?

Answer 5

0 degrees phase difference between two two waves that interact (360, 720)
Path difference is a multiple of the wavelength

Question 6

What are the conditions for destructive interference ?

Answer 6

Phase difference of 180 degrees ( waves must be in antiphase )
Path difference = (n+1/2) lamda

Question 7

What is antiphase ?

Answer 7

Peak will meet at a trough

Question 8

Youngs double slit experiment requirements

Answer 8

Two coherent waves are needed
Monochromatic source of light was originally used
The slit needs to be narrow

Question 9

Young double slit experiment described

Answer 9

The lamp releases some light that goes through the filter so it ensures we have monochromatic light
It reaches the first slit where they will diffract
Encounters two further slits where they r diffracted again and serves as two separate sources

Question 10

How to reduce uncertainty with the experiment ?

Answer 10

Increase the distance D to a maximum which reduces p.d.
Measure the distance between multiple fringes and then divide by that number

Question 11

State the effect on the fringes if distance to the screen increased

Answer 11

Fringe separation increases as it is directly proportional to the distance provided that the wavelength and the slit separation remain constant

Question 12

What would happen if the speakers are swapped ?

Answer 12

The maxima would turn into minima and fuse versa

Question 13

Experiment to determine the wavelength of light using a double slit

Answer 13

Measure the distance to the screen and the fringe separation with a ruler the slit separation with a travelling microscope
Very the distance d and measure the fringe separation
Plot a graph of s against d