With what velocity must an electron travel so that its momentum is equal to that of a photon of wavelength of `lamda =5000 Å` ?

Explanation

Momentum `=mv and lamda =h//mv.` They are the momentum of an electron and photon respectively. Thus by equating them would give the velocity.
`because lamda = h/mv`, Momentum of photon `=mv=h//lamda =(6.626xx10^(-34))/(5000xx10^(-10)) kg" ms"^(-1)`
Also, momentum of electron `=mv =9.108xx10^(-31)xx v" kg ms"^(-1)`
Equating `9.108xx10^(-31) xx v=(6.626xx10^(-34))/(5000xx10^(-10))" or "v=(6.626xx10^(-34))/(9.108xx10^(-31)xx5000xx10^(-10))=1455 ms^(-1)`