Question

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

Answer 1

De-Broglie wavelength `lambda=h/(mv) or lambda prop 1/m` if v is constant. Then `(lambda_p)/(lambda_e)=(m_e)/(m_p) lt 1` or `lambda_p lt lambda_e`
i.e., De-Broglie wavelength of electron is more than that of proton.