The kinetic energy of a proton and that of an a-particle are 4 eV and 1 eV,
respectively. The ratio of the de-Broglie wavelengths associated with
them, will be
(a) 2:1
(b) 1:1
(c) 1:2
(d) 4:1

Explanation:

1. Formulae:

Where:

2. Reasoning

An alha particle contains 2 neutrons and 2 protons, thus its mass number is 4.

A proton has mass number 1.

Thus, the relative masses of an alpha particle and a proton are:

For the kinetic energies you find:

Thus:

From de-Broglie equation, λ = h/(mv)  

f is prop to m1xm2 double m1 double force