Dual Nature Of Light Question 312
Question: A caesium photocell, with a steady potential difference of 60V across, is illuminated by a bright point source of light 50 cm away. When the same light is placed 1m away the photoelectrons emitted from the cell [KCET 2002]
Options:
A) Are one quarter as numerous
B) Are half as numerous
C) Each carry one quarter of their previous momentum
D) Each carry one quarter of their previous energy
Show Answer
Answer:
Correct Answer: A
Solution:
Number of photo electrons (N) µ Intensity $ \propto \frac{1}{d^{2}}\Rightarrow \frac{N_{1}}{N_{2}}={{( \frac{d_{2}}{d_{1}} )}^{2}} $
$ \Rightarrow \frac{N_{1}}{N_{2}}={{( \frac{100}{50} )}^{2}}=\frac{4}{1}\Rightarrow N_{2}=\frac{N_{1}}{4} $ .
BETA
