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Question: A cesium photocell with a steady potential difference of 60 V across it is illuminated by a small br...

A cesium photocell with a steady potential difference of 60 V across it is illuminated by a small bright light placed 1 m away. When the same light is placed 2m away, the electrons crossing the photocell –

A

Each carry one-quarter of their previous momentum

B

Each carry one-quarter of their previous energy

C

Are one-quarter as numerous

D

Are half as numerous

Answer

Are one-quarter as numerous

Explanation

Solution

i ∝

i2i1\frac { i _ { 2 } } { i _ { 1 } }= = (12)2\left( \frac { 1 } { 2 } \right) ^ { 2 } = 14\frac { 1 } { 4 }i2 = i14\frac { i _ { 1 } } { 4 }

n2 = n14\frac { \mathrm { n } _ { 1 } } { 4 }