Question

Can interference patterns be produced by two independent monochromatic light sources ? Explain your answer.

Answer 1

For a successful interference pattern two conditions must necessarily be met:
(i) The sources must be coherent in nature.
(ii) The sources must be monochromatic in nature.

Complete step by step solution:
Interference is a phenomenon in physics, where two waves superimpose on each other to form a resultant wave, whose amplitude is greater than , less than or equal to the superimposing waves.

We know that for interference patterns to be obtained, The sources must be coherent, which means that they must continuously emit waves. When they are not coherent they cannot emit waves continuously and thus cannot give rise to interference.

Another major factor that is necessary for interference to occur is that the waves must be at the same phase or constant phase difference. However, this is not a characteristic of independent sources.

Independent sources imply they emit waves which are not in the same or constant phase difference, thus in the given case interference pattern is not observed.

In incoherent sources, the waves do not differ by a constant phase difference and are not not same phase as well, thus the condition for interference is violated.

Thus, the sources being independent in nature although being monochromatic, cannot produce interference patterns.

Additional Information:
The resultant wave after interference may be greater in amplitude, it is known as Constructive Interference. The resultant Wave after interference if is lesser in amplitude, it is known as Destructive Interference.

Note: The sources in spite of being monochromatic do not produce interference as they are independent. Interference must at least have two sources of light which are coherent and monochromatic in nature.