Question

The phenomenon of diffraction can be treated as an interference phenomenon if the number of coherent sources is__________.
A. one
B. two
C. zero
D. infinity

Answer 1

Diffraction grating is a component of optical devices consisting of a surface ruled with close, equidistant, and parallel lines. It is commonly used for the purpose of resolving light into spectra. When light falls on diffraction grating, it disperses the light in a pattern similar to that of double slit interference.

Complete answer:
Diffraction grating is a component of optical devices consisting of a surface ruled with close, equidistant, and parallel lines.
When light is passed through a large number of evenly spaced parallel slits, an interesting thing happens, an interference pattern is created that is very similar to the one formed by a double slit. The diffraction pattern will be more similar if the number of slits tends to be infinite. That is, the phenomenon of diffraction can be treated as an interference phenomenon if the number of coherent sources is infinite.

So, the correct answer is “Option D”.

Additional Information:
Light is an electromagnetic wave. Interference and diffraction are the phenomena occurring to all types of waves. Interference is the phenomena observed due to superimposing of two coherent waves while diffraction is the phenomena of bending of waves at the edges of a particle of size comparable to wavelength of the wave.
Interference has many applications. It is used to test surface qualities, in radio astronomy, measuring light intensity etc.

Note:
Diffraction gratings can either be transparent or mirrored. A grating is known as a transmission or reflection grating according to whether it is transparent or mirrored.
There is constructive interference for a diffraction grating when $d\sin \theta =m\lambda$(m must be an integer), where d is the distance between slits in the grating, $\lambda$ is the wavelength of light, and m is the order of the maximum.