Question

An electron, an alpha particle and a proton have the same kinetic energy.

Which one of these particles has the largest de-Broglie wavelength? 

Answer 1

De-Broglie’s wavelength is given as, λ = `h/(sqrt(2mK))`

Where, h is Planck’s constant, m is the mass of the particle, K is the kinetic energy of the particle

The mass of the electron is least among an electron, an alpha particle, and a photon.

`because lambda ∝ 1/sqrtm`, therefore, the electron has the largest de-Broglie wavelength.