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Solution


Q.

If ϕ is the work function of photosensitive material in eV and light of wavelength of numerical value λ=hce metre, is incident on it with energy above its threshold value at an instant, then the maximum kinetic energy of the photo-electron ejected by it at that instant (Take h - Planck’s constant, c - velocity of light in free space) is (in SI units)   [2024]
 
1 e+2ϕ  
2 2e-ϕ  
3 e-ϕ  
4 e+ϕ  

Ans.

(3)

According to Einstein photoelectric equation,

Photon energy=K.E.+Work function

Here, photon energy =e eV

Work function =ϕ eV

∴   e=K.E.+ϕ  ⇒  K.E.=e-ϕ