Q 1 :

A proton has kinetic energy E=100 keV which is equal to that of a photon. The wavelength of the photon is λ2 and that of the proton is λ1. The ratio λ2λ1 is proportional to                [2004]

  • E2

     

  • E1/2

     

  • E-1

     

  • E-1/2

     

(4)

For photon,  λ2=hcE                                                            ⋯(i)

For proton,  λ1=hp=h2mE      ∵  p=2mE        ⋯(ii)

∴  λ2λ1=hcE×h2mE∝E-1/2



Q 2 :

An α-particle and a proton are accelerated from rest by a potential difference of 100 V. After this, their de Broglie wavelengths are λα and λp, respectively. The ratio λpλα, to the nearest integer, is                          [2010]



(3)

We know that,  λ=h2mqV  or,  λ∝1qm

∴  λpλα=mαqαmpqp=41×21=8≈3