Question

The threshold frequency of a metal is $f _0$ When the light of frequency $2 f _0$ is incident on the metal plate, the maximum velocity of photoelectrons is $v_1$ When the frequency of incident radiation is increased to $5 f _0$, the maximum velocity of photoelectrons emitted is $v_2$ The ratio of $v_1$ to $v_2$ is :

• A. $\frac{v_1}{v_2}=\frac{1}{8}$
• B. $\frac{v_1}{v_2}=\frac{1}{4}$
• C. $\frac{v_1}{v_2}=\frac{1}{16}$
• D. $\frac{v_1}{v_2}=\frac{1}{2}$

Answer 1

Answer: (D)

$\frac{v_1}{v_2}=\frac{1}{2}$

Answer 2

Kmax​=hf−hf0​
For f=2f0​
21​mV12​=2h0​−hf0​=hf0​
For f=5f0​
21​mV22​=5hf0​−hff0​=4hff0​
V2​V1​​=21​