Q.

A proton of mass 'mp' has same energy as that of a photon of wavelength 'λ'. If the proton is moving at non-relativistic speed, then ratio of its de-Broglie wavelength to the wavelength of photon is.          [2025]

1 1c2Emp  
2 1cEmp  
3 1cE2mp  
4 12cEmp  

Ans.

(3)

E is missing in the question but considering E as energy.

Energy of photon, Ephoton=hcλphoton

 Wavelength of photon, λphoton=hcE

Energy of proton, Eproton=12mpv2=p22mp

 Linear momentum of proton, p=2mpE

or de-Broglie wavelength of proton, λproton=hp=h2mpE

Ratio λprotonλphoton=h2mpE×Ehc=1cE2mp