What is a diffraction grating?

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:

In Fraunhoffer diffraction for single slit central maxima is bright on the both side of it, maxima & minima occurs symmetrically.



For Diffraction Maxima: $a\; sin\theta =\left(2n+1\right)\frac{\lambda }{2}$
For Diffraction Minima: $a\; sin\theta =\text{n}\lambda$

Light of wavelength $\lambda$ passes through a single slit of width $W$ and forms a diffraction pattern on a viewing screen. If this light is then replaced by light of wavelength $2\lambda$, the original diffraction pattern is exactly reproduced if the width of the slit is changed to