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:

Assertion A states that an electron microscope can achieve better resolving power than an optical microscope. This is true because the resolving power of a microscope is inversely proportional to the wavelength of the radiation used, and electron beams have much shorter wavelengths than visible light.

Reason R states that the de Broglie wavelength of electrons emitted from an electron gun is much less than the wavelength of visible light. This is true. For example, electrons accelerated through a potential difference of 100 V have a de Broglie wavelength of about 0.12 nm, which is far smaller than visible light wavelengths (400-700 nm).

Since the resolving power improves with shorter wavelength, the fact that electrons have much shorter de Broglie wavelengths (Reason R) directly explains why electron microscopes achieve better resolving power (Assertion A).

Therefore, both A and R are true, and R is the correct explanation of A.

Hence the correct answer is Option 2.