Question

The main difference in the phenomenon of interference and diffraction is that :-
A) Diffraction is due to interaction of light from the same wavefront whereas interference is the interaction of (light) waves from two isolated sources.
B) Diffraction is due to interaction of light from the same wavefront whereas interference is the interaction of two waves derived from the same source.
C) Diffraction is due to interaction of waves derived from the same source, whereas interference is the bending of light from the same waveform.
D) Diffraction is caused by the reflected waves from a source whereas interference is caused due to waves from a source.

Answer 1

Hint: The simplest approach to solve this question is to try to recall what interference and diffraction are. Interference, as the name suggests, is the phenomenon related to interference of two different light waves while diffraction is due to lights from the same wavefront.

Complete step by step answer:
As explained in the hint section of the solution to this question, we will start solving the question by first defining and explaining the terms interference and diffraction.
Let us start by defining diffraction:
If a plane wave is passed through a small hole, spherical waves are obtained on the other side as if the hole itself is a source sending waves in all directions. Such bending of waves from an obstacle or an opening is called diffraction. We can clearly observe that this must happen with the light from the same wavefront. In other words, secondary wavelets of a wave which originate from different parts of the same wavefront make the diffraction possible.
Now, we will define interference:
Interference is the process of superimposition of two or more waves with the same frequency emitted by coherent but different sources with a condition that amplitude of resultant wave is equal to the sum of the amplitude of the individual waves. Coherent sources are the sources which have a constant phase difference which is a constant value. Frequencies of coherent sources must also match each other.
Now that we have defined both of the given terms, we can clearly see that the correct option is option (A) which states that diffraction is due to interaction of light from the same wavefront whereas interference is the interaction of (light) waves from two isolated sources.

Note: Many students consider diffraction only as the process of bending of light or wave when it encounters a small obstacle. Although this is correct but since the question has no such option, you need to find the answer by manipulating this fact and thinking of diffraction from a different perspective.