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Question: Light of wavelengths \(\lambda\) falls on a metal having works function \(\frac { \mathrm { hc } }...

Light of wavelengths λ\lambda falls on a metal having works function hcλ0\frac { \mathrm { hc } } { \lambda _ { 0 } } Photoelectric effect will take placed only:

A

λ≥λ0\lambda \geq \lambda _ { 0 }

B

λ≤λ0\lambda \leq \lambda _ { 0 }

C

λ≥2λ0\lambda \geq 2 \lambda _ { 0 }

D

λ=4λ0\lambda = 4 \lambda _ { 0 }

Answer

λ≤λ0\lambda \leq \lambda _ { 0 }

Explanation

Solution

: As kinetic energy K=hcλ−hcλ0K = \frac { h c } { \lambda } - \frac { h c } { \lambda _ { 0 } }

K is positive, therefore photoelectric emission will take place if hcλ≥hcλ0\frac { h c } { \lambda } \geq \frac { h c } { \lambda _ { 0 } } or λ≤λ0\lambda \leq \lambda _ { 0 }