Wave Interference

Question 1

Interference

Answer 1

Interference happens when any two waves are superimposed on one another.
But in most cases, this creates a very messy wave pattern.
To see a clear interfernce pattern, we need two waves that are coherent.

Question 2

Coherent

Answer 2

• It means that the two waves must have the same frequency and wavelength, and have a fixed phase relation.
• Usually this fixed phase relation is zero

Question 3

Principle of superposition

Answer 3

When waves from two sources arrive at the same place then they add together
If they arrive in phase - constructive interference
If they arrive in anti - phase - destructive interference , for example
- Large and small water ripples
- Light and dark fringes (visible light)
- Loud and soft (sound)
- good and poor reception (radio/phone)

Question 4

Superposition

Answer 4

It is the addition of waves of the same type that are in the same place

1. Constructive superposition - when two waves add up to make a larger wave.
2. Total destructive superposition - when the waves cancel each other out completely. This happens if a peak and a trough meet.
3. Partial destructive superposition - when the waves cancel each other out to make a smaller wave.

Question 5

Constructive interference

Answer 5

If the waves arrive in phase then they interfere constructively.

Question 6

Destructive interference

Answer 6

If the waves arrive in anti - phase then they will interfere destructively.

Question 7

Path difference

Answer 7

It is the difference in the distances that two waves travel before they hit a screen.
It is created by dividing a light source so the separate rays of light travel different paths.
Bigger angles have larger path differences
Smaller angles have smaller path differences