Question

$A$ and $B$ are two metals with threshold frequencies $1.8\times {10}^{14}$$Hz$ and $2.2\times {10}^{14}$$Hz$. Two identical photons of energy $0.825$$eV$ each are incident on them. Then photoelectrons are emitted by:
(Taking $h=6.626\times {10}^{-34}$$Js$)

• A. $B$ alone
• B. $A$ alone
• C. Neither $A$ nor $B$
• D. Both $A$ and $B$

Answer 1

Answer: (B)

$A$ alone

Frequency of photon corresponding to energy $0.825eV=\frac{0.825\times 1.6\times {10}^{-19}}{6.626\times {10}^{-34}}=1.99\times {10}^{14}Hz$

Since, this frequency is greater than the frequency required for emission of photoelectrons from metal $A$, photoelectrons are emitted from metal $A$ but not from metal $B$.