Question

Two identical photocathode receives light of frequencies andif the velocities of the photoelectrons (of mass m) coming out are respectively and then

• A.
• B.
• C.
• D.

Answer 1

Answer: (A)

Answer 2

: According to Einstein’s equation

Kinetic energy of emitted electron

$= h v - ($ work function $\phi )$

$\therefore \frac { 1 } { 2 } m v _ { 1 } ^ { 2 } = h v _ { 1 } - \phi$ $\frac { 1 } { 2 } m v _ { 2 } ^ { 2 } = h v _ { 2 } - \phi$ $\therefore \frac { 1 } { 2 } m \left( v _ { 1 } ^ { 2 } - v _ { 2 } ^ { 2 } \right) = h \left( v _ { 1 } - v _ { 2 } \right)$

$\therefore v _ { 1 } ^ { 2 } - v _ { 2 } ^ { 2 } = \frac { 2 h } { m } \left( v _ { 1 } - v _ { 2 } \right)$