Question

A photoelectric emitter has a threshold frequency ${\vartheta }_0$. When light frequency $2{\vartheta }_0$ is incident, the speed of photoelectrons is V. When the light of frequency $10{\vartheta }_0$. is incident the speed of photoelectrons will be:

• A. $5V$
• B. $3V$
• C. $20V$
• D. $8V$

Answer 1

The correct option is B $3V$

Given that,

$2h{\vartheta }_0=h{\vartheta }_0+\frac{1}{2}m{v}^2$

$\Rightarrow h{\vartheta }_0=\frac{1}{2}m{v}^2$
Again,

$10h{\vartheta }_0=h{\vartheta }_0+\frac{1}{2}m{v}^2$

$\Rightarrow 9h{\vartheta }_0=\frac{1}{2}m{v}^2$

$\Rightarrow v=3V$

Option B is correct.