Optics Question 510
Question: A point source of light moves in a straight line parallel to a plane table. Consider a small portion of the table directly below the line of movement of the source. The illuminance at this portion varies with its distance r from the source as
Options:
A) $ E\propto \frac{1}{r} $
B) $ E\propto \frac{1}{r^{2}} $
C) $ E\propto \frac{1}{r^{3}} $
D) $ E\propto \frac{1}{r^{4}} $
Show Answer
Answer:
Correct Answer: C
Solution:
$ I=\frac{Lh}{r^{3}} $
