Assertion: For the scattering of `alpha`-particles at a large angles, only the nucleus of the atom is responsible.
Reason: Nucleus is very heavy in comparison to electrons.

Options

A. if both assertion and reason are true and reason is the correct explanation of assertion.
B. if both assertion and reason are true but reason is not the correct explanation of assertion.
C. if assertion is true but reason is false.
D. if both assertion and reason are false.

Answer

A

Explanation

we know that an electron is very light particle as compared to an `alpha`-particle. Hence electron cannot scatter the `alpha`-particle at large angles, according to law of conservation of momentum. On the other hand, mass of nucleus is comparable with the mass of `alpha`-particle, hence only the nucleus of atom is responsible for scattering of `alpha`-particles.