A and B are two metals with threshold frequencies `1.8 xx 10^(14)`Hz and `2.2 xx 10^(14)` Hz.Two identical photons of energy `0.825` eV each are incident on them.Then photoelectrons are emitted in
(Take `h = 6.6 xx 10^(34)` Js)

Options

A. B alone
B. A alone
C. neither A nor B
D. both A and B

Answer

B

Explanation

Photoelectrons are emitted in A alone. Energy of electron needed if emitted from `A = (h upsilon)/(e) eV`
`therefore E_(A) = (6.6 xx 10^(-34) xx (1.8 xx 10^(14)))/(1.6 xx 10^(-19)) = 0.74 eV`
Again `E_(B) = (6.6 xx 10^(-34) xx (2.2 xx 10^(14)))/(1.6 xx 10^(-19)) = 0.91 eV`
Incident energy `0.825` eV is greater than `E_(A) (0.74 eV)` but less than `E_(B) (0.91 eV)` Hence, photoelectrons are emitted in A alone .