A photocell is illuminated buy asmall bright source places `1` m away when the same source oh light is placed `(1)/(2) m away. The number of electron emitted by photocathode would
A
increase by a factor of `4`
B
decrease by a factor of `4`
C
increase by a factor of `2`
D
decrease by a factor of `4`
Text Solution
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The correct Answer is:
A
1 prop (1)/(r^(2)), (1_(1))/(1_(2)) = ((r_(2))/(r_(1)))^(2) = (1)/(4)` `I_(2) rarr 4 times I_(1)` When intesity become `4 times` , no of photoelectrons emitted would increases by `4 time`, since number of electrons emitted per second is directly proportional to intensity
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