First slide

Photoelectric effect and study of photoelectric effect

Question

Given that a photon of light of wavelength 10,000 $Å$ has an energy equal to 1.23 eV. When light of wavelength 5000 $Å$ and intensity I_o falls on a photoelectric cell,
the saturation current is 0.40 x 10^-6 A and the stopping potential is 1.36 V; if the wavelength is changed to 4000 $Å$ , then stopping potential will become

Moderate

A

1.36 V
B

3.40 V
C

1.60 V
D

1.97 V

Solution

Let energy corresponding to wavelength of 4000 $Å$ be E. Then,
$\begin{array}{l} \frac{E}{E^{'}} = \frac{λ^{'}}{λ} or \frac{E}{1.23} = \frac{10, 000}{5000} \\ \Rightarrow E = 1.23 \times 2 = 2.46 eV \end{array}$
$\begin{array}{l} \begin{array}{l} But h v - h v_{0} = e V_{s} \\ or 2.46 eV - 1.36 eV = W \Rightarrow W = 1.1 e V \end{array} \\ \Rightarrow \frac{E}{E^{'}} = \frac{λ^{'}}{λ} or \frac{E}{1.23} = \frac{10, 000}{4000} \end{array}$
$\begin{array}{l} ∴ E = 1.23 \times 2.5 = 3.075 eV \\ But h v - h v_{0} = e V_{s} \\ or 3.075 eV - 1.1 eV = e V_{s} \\ ∴ V_{s} = 1.975 V \end{array}$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App