What do you mean by diffraction of light? Why diffraction of sound waves are easily observed than diffraction of light waves? Compare Fresnel's and Fraunhofer diffraction. 

What is diffraction of light?

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Diffraction of light.

In the figure below, $P$ and $Q$ are two equally intense coherent sources emitting radiation of wavelength $20\mathrm{m}.$ The separation between $\mathrm{P}$ and $\mathrm{Q}$ is $5\mathrm{m}$ and the phase of $\mathrm{P}$ is ahead of that of $\mathrm{Q}$ by $90°.\mathrm{A},\mathrm{B}$ and C are three distinct point of observation, each equidistant from the midpoint of PQ. The intensities of radiation at $\mathrm{A},\mathrm{B},\mathrm{C}$ will be in the ratio :

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A : An electron microscope can achieve better resolving power than an optical microscope.

Reason R : The de Broglie's wavelength of the electrons emitted from an electron gun is much less than wavelength of visible light.

In the light of the above statements, choose the correct answer from the options given below:

The position of the direct image obtained at $O,$ when a monochromatic beam of light is passed through a plane transmission grating at normal incidence is shown in figure. The diffracted images $\mathrm{A}, \mathrm{B}$ and $\mathrm{C}$ correspond to the first, second and third order diffraction. When the source is replaced by another source of shorter wavelength