Question

Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material. What will be the photoelectric current if the frequency is halved and intensity is doubled?

• A. doubled
• B. four times
• C. one-fourth
• D. zero

Answer 1

Answer: (D)

$K_{1}=1.5 \,hv_{0}-\phi_{0}=0.5\,hv_{0}$
$K_{2}=\frac{1.5}{2}hv_{0}-hv_{0}=-0.25\,hv_{0}$
$\because$ Kinetic energy can never be negative, so no emission and $i=0$