Dual Nature Of Light Question 92
Question: 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 [IIT JEE 1992; MP PMT 1999]
Options:
A) The stopping potential will be 0.2 V
B) The stopping potential will be 0.6 V
C) The saturation current will be 6 mA
D) The saturation current will be 18 mA
Show Answer
Answer:
Correct Answer: B
Solution:
Cut off voltage is independent of intensity and hence remains the same. Since distance becomes 3 times, so intensity (I) becomes $ \frac{I}{9}. $ Hence photo current also decreases by this factor i.e. becomes $ \frac{18}{9}=2,mA. $
BETA
