Question 197: Dual Nature of Matter and Radiation

Question

A photoelectric surface is illuminated successively by monochromatic light of wavelengths $\lambda $ and ${\lambda  \over 2}.$ If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function of the surface is :

Accepted Answer

We know,
Einstein's photo electric equation,
(KE)
max
= ${{hc} \over \lambda }$ $-$ $\phi $
0
In first case,
K = ${{hc} \over \lambda }$ $-$ $\phi $
0
. . .(1)
In second case,
3K = ${{2hc} \over \lambda }$ $-$ $\phi $
0
. . .(2)
$ \Rightarrow $   $3\left( {{{hc} \over \lambda } - {\phi _0}} \right)$ = ${{2hc} \over \lambda } - {\phi _0}$
$ \Rightarrow $   ${{3hc} \over \lambda }$ $-$ 3$\phi $
0
= ${{2hc} \over \lambda }$ $-$ $\phi $
0
$ \Rightarrow $   ${{hc} \over \lambda }$ = 2$\phi $
0
$ \Rightarrow $   $\phi $  =  ${{hc} \over {2\lambda }}$

Answer

${{hc} \over {3\lambda }}$

Answer

${{hc} \over {2\lambda }}$

Answer

${{hc} \over {\lambda }}$

Answer

${3\,{hc} \over {\lambda }}$

Dual Nature of Matter and Radiation

A photoelectric surface is illuminated successively by monochromatic light of wavelengths \lambda and {\lambda \over 2}. If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function of the surface is :

Choose the correct answer: