Question

When a certain photosensitive surface is illuminated with monochromatic light of frequency $v$, the stopping potential for the photocurrent is $\frac{V_0}{2}$. When the surface is illuminated by monochromatic light of frequency $\frac{v}{2}$, the stopping potential is $-V_0$. the threshold frequency for photoelectric emission is:

• A. $\frac{3v}{2}$
• B. $2v$
• C. $\frac{4}{3}v$
• D. $\frac{5v}{3}$

Answer 1

Answer: (A)

$\frac{3v}{2}$

$h\nu =W+\frac{v_o}{2}e$

$\frac{h\nu }{2}=W+v_{o}e$

on solving we get, $W=3/2h\nu$

$h{v}_o=3/2h\nu$

$v_o=3/2v$