When a monochromatic point source of light is at a distance 0.2 m from a photoelectric cell, the cut-off voltage and the saturation current are respectively, 0.6 volt and 18.0 mA. If the same source is placed 0.6 m away from the photoelectric cell, then i) VS=0.2 V ii) VS=0.6 V iii) i=6 mA iv) i=2.0 mA

Question

When a monochromatic point source of light is at a distance 0.2 m from a photoelectric cell, the cut-off voltage and the saturation current are respectively, 0.6 volt and 18.0 mA. If the same source is placed 0.6 m away from the photoelectric cell, then i) VS=0.2 V ii) VS=0.6 V iii) i=6 mA iv) i=2.0 mA (A) (i),(ii) (B) (ii),(iii) (C) (i),(iv) (D) (ii),(iv)

Tardigrade Admin · Accepted Answer

Stopping potential is independent of intensity i propto I ⇒ (i2/i1)=(I2/I1)=((r1/r2))2 ⇒ i2=i1 ×((0.2/0.6))2 =18 × (1/9)=2 m A

(i),(ii)

(ii),(iii)

(i),(iv)

(ii),(iv)

Stopping potential is independent of intensity i∝I⇒i1​i2​​=I1​I2​​=(r2​r1​​)2 ⇒i2​=i1​×(0.60.2​)2 =18×91​=2mA

Stopping potential is independent of intensity
$i \propto I \Rightarrow \frac{i _{2}}{i _{1}} = \frac{I _{2}}{I _{1}} = (\frac{r _{1}}{r _{2}})^{2}$
$\Rightarrow i_{2} = i_{1} \times (\frac{0.2}{0.6})^{2}$
$= 18 \times \frac{1}{9} = 2 m A$