Question

A proton and an electron have same kinetic energy. Which one has greater de-Broglie wavelength and why?

Answer 1

The de Broglie wavelength of a particle is inversely proportional to its momentum p = m v; since a proton is about 1800 times more massive than an electron, its momentum at the same speed is 1800 times that of an electron, and therefore its wavelength 1800 times smaller. The electron has the longer wavelength