A point source is kept at the center of a spherically enclosed detector. If the volume of the detector is increased by 8 times, the intensity will
- increase by 64 times
- decrease by 4 times
- decrease by 8 times
- increase by 8 times
Answer
(2) decrease by 4 times
Solution
V = 43 R3; V' = 8V R'3 = 8R3 R' = 2R
For a point source of power P: I = P4 R2 I 1R2
I'I = ( RR' )2 = 14
The intensity decreases by 4 times.
Answer: (2)