Question

The work function for sodium surface is 2.0 eV and that for the aluminium surface is 4.2 eV. The two metals are illuminated with appropriate radiations so as to cause photoemission. Then

• A. The threshold frequency for sodium will be less than that for aluminium
• B. The threshold frequency for sodium will be more than that for aluminium
• C. Both sodium and aluminium will have the same threshold frequency
• D. None of the above

Answer 1

Answer: (A)

The threshold frequency for sodium will be less than that for aluminium

The relation between work function $\left(W\right)$ and threshold frequency $\left({\nu }_0\right)$ is given by,

$W=h{\nu }_0$ where $h=$ Planck's constant

As $W_{Na}<W_{Al}$ so ${\nu }_0\left(Na\right)<{\nu }_0\left(Al\right)$