Question

Can two identical and independent sodium lamps act as coherent sources?

Answer 1

Hint:In order to solve this question, we should know that Coherent source is those that emit waves of the same frequency, and wavelength and are in the same or constant phase difference, here we will discuss the coherence nature of two identical and independent sodium lamp.

Complete answer:
As we know, Sodium Lamps are gas discharge lamps that use sodium atoms in an excited state to produce light waves. so when two different sodium lamp emits light wave then atoms that emit the light vibrate at their own frequency which can never be the same no matter how we make two sources exactly identical because there can never be a hundred percent efficiency such that two atoms can have same vibrational phase and this difference in phase of the atoms can never produce two waves which will have the same phase difference. So when we made two sodium lamps exactly the same but independent then due to their vibrational frequency phase difference they can’t emit light waves which can have the same phase difference.

Hence, due to the difference in the vibrational frequency of atoms of different sodium lamps, two sodium lamps that are identical and independent can never act as coherent sources.

Note: It should be remembered that we can certainly produce coherent sources using a single source by splitting of the wave using two slits and making secondary waves coherent and it’s the best possible way to make two sources coherent.