A photocell is illuminated by a small bring source placed $1 m$ away. When the same source of light is placed $1 / 2 m$ away, the number of electrons emitted by photocathode would :

Decrease by a factor of 4

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Increase by a factor of 4

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Decrease by a factor of 2

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Increase by a factor of 2

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Solution

The correct option is C Increase by a factor of 4
Since Intensity $(I) α \frac{1}{r^{2}}$

When distance become half, intensity becomes $4$ times. Hence number of electrons increases by factor of $4$ . The number of electrons emitted of photo cathode would increase by a factor of $4$ .

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A photocell is illuminated by a small bring source placed 1m away. When the same source of light is placed 1/2 m away, the number of electrons emitted by photocathode would :

The correct option is C Increase by a factor of 4Since Intensity (I)α1r2When distance become half, intensity becomes 4 times. Hence number of electrons increases by factor of 4. The number of electrons emitted of photo cathode would increase by a factor of 4.

A photocell is illuminated by a small bring source placed $1 m$ away. When the same source of light is placed $1 / 2 m$ away, the number of electrons emitted by photocathode would :

The correct option is C Increase by a factor of 4
Since Intensity $(I) α \frac{1}{r^{2}}$

When distance become half, intensity becomes $4$ times. Hence number of electrons increases by factor of $4$ . The number of electrons emitted of photo cathode would increase by a factor of $4$ .