Top – Monochromatic light
Bottom: White light
To obtain an observable interference pattern using two sources, there must be:
- Coherent sources: so that a constant interference pattern can be obtained.
- Equal or approximately equal amplitude: so that complete or almost complete cancellation is achived at points of destructive interference
- Polarised in same plane(or both unpolarised) : If the waves are not polarised in the same plane, then complete cancellation is not possible even at points where the two waves are completely out of phase.
