1. Tardigrade
  2. Question
  3. Physics
  4. When a point source of monochromatic light is at a distance of 0.2 m from a photoelectric cell, the cut-off voltage and the saturation current are 0.6 volt and 18 mA respectively. If the same source is placed 0.6 m away from the photoelectric cell, then

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Q. When a point source of monochromatic light is at a distance of $0.2\, m$ from a photoelectric cell, the cut-off voltage and the saturation current are $0.6$ volt and $18\, mA$ respectively. If the same source is placed $0.6\, m$ away from the photoelectric cell, then

Dual Nature of Radiation and Matter

Solution:

Cut-off voltage is independent of intensity and hence, remains the same.
Since distance becomes $3$ times, intensity $(I)$ becomes $\frac{I}{9}$.
Hence, photocurrent also decreases by this factor
i.e., becomes $\frac{18}{9}=2\, mA$.