When the wavelength of radiation falling on a metal is changed from

Question:

When the wavelength of radiation falling on a metal is changed from $500 \mathrm{~nm}$ to $200 \mathrm{~nm}$, the maximum kinetic energy of the photoelectrons becomes three times larger. The work function of the metal is close to :

  1. (1) $0.81 \mathrm{eV}$

  2. (2) $1.02 \mathrm{eV}$

  3. (3) $0.52 \mathrm{eV}$

  4. (4) $0.61 \mathrm{eV}$


Correct Option: , 2

Solution:

(2)

Using equation, $=\frac{h c}{\lambda}-\phi$

$K E_{\max }=\frac{h c}{\lambda}-\phi=\frac{h c}{500}-\phi$          ....(1)

Again, $3 K E_{\max }=\frac{h c}{200}-\phi$                                    ....(2)

Dividing equation (2) by (1),

$\frac{3 K E_{\max }}{K E_{\max }}=\frac{3}{1}=\frac{\frac{h c}{200}-\phi}{\frac{h c}{500}-\phi}$

Putting the value of $h c=1237.5$ and solving we get, work function, $\phi=0.61 \mathrm{eV}$.

Leave a comment

Close
faculty

Click here to get exam-ready with eSaral

For making your preparation journey smoother of JEE, NEET and Class 8 to 10, grab our app now.

Download Now