3.8 Two-Source Interference

Question 1

What is two-source interference?

Answer 1

When the waves from two sources interfere to produce a pattern

Question 2

What properties do waves need to have to produce a clear interference pattern?

Answer 2

The waves from the two sources must be monochromatic and coherent

Question 3

What do two waves need to be coherent?

Answer 3

Two waves are coherent if they have the same wavelength and frequency and a fixed phase difference between them

Question 4

What happens when coherent light sources interfere?

Answer 4

Clear patterns of constructive and destructive interference are seen

Question 5

What determines whether you get constructive or destructive interference at a point?

Answer 5

How much further one wave has travelled than the other wave to get to that point

Question 6

What is path difference?

Answer 6

The amount by which the path travelled by one wave is longer than the path travelled by the other wave

Question 7

What are maxima?

Answer 7

Points at which total constructive interference occurs

Question 8

When do maxima happen?

Answer 8

At any points an equal distance from two sources in phase or where the path difference is a whole number of wavelengths

Question 9

What are minima?

Answer 9

Points at which total destructive interference occur

Question 10

When do minima happen?

Answer 10

At points where the path difference is half a wavelength, one and a half wavelengths, etc, the waves arrive out of phase and you get total destructive interference