KVPY Sample Paper KVPY Stream-SX Model Paper-6

When a certain photosensitive surface is illuminated with monochromatic light of frequency v, the stopping potential for the photo current is \[-{{\text{V}}_{\text{0}}}\text{/}2.\] When the surface illuminated by monochromatic light of frequency \[\text{V/2},\]the stopping potential is \[-{{V}_{0}}.\] The threshould Frequency for photoelectric emission is:

A) \[\frac{5v}{3}\]

B) \[\frac{4}{3}v\]

C) \[2v\]

D) \[\frac{3v}{2}\]

Correct Answer: D

Solution :

\[e{{V}_{s}}=hv-\phi \]
\[\left\{ \frac{-e{{V}_{o}}}{2}=h\nu -\phi \right\}\times 2\]	? (1)
\[e{{V}_{s}}=\frac{h\nu }{2}-\phi \]	? (2)
\[0=2hv-2\phi -\frac{hv}{2}+\phi \]
\[\phi =\frac{3h\nu }{2}\]
\[\Rightarrow \] \[{{\nu }_{th}}=\frac{3\nu }{2}.\]