Question

Why cannot we obtain interference using two independent sources of light ?

Answer 1

Coherent sources

• Two waves are said to be coherent when the phase difference between them is constant.
• They are non-coherent if there is random or changing phase.
• We can obtain interference only using coherent waves.

We cannot obtain interference using two independent sources of light because:

• Two independent sources of light cannot be coherent because they cannot emit wave continuously
• The two independent sources of light will not have same phase or constant phase difference between them.
• They will have random phase difference between them.