Energy of X-ray photon Ephoton=50keV=5×104eV
Energy equivalent of electron mass is 0.5MeV i.e mc2=0.5MeV=5×105eV ......(1)
Wavelength of the photon λphoton=hcE=12425×104 nm=0.0248 nm
∴ de-Broglie wavelength of the electron λ=λphoton=0.0248 nm
Kinetic energy of electron Eelectron=h22m×λ2=h2c22(mc2)λ2 (∵E=p22m)
Kinetic energy of electron Eelectron=(1242)22(5×105)×(0.0248)2 eV=2.51×103eV
∴ EphotonEelectron=5×1042.51×103=20