Optics Question 495
Question: A lamp is hanging 1 m above the centre of a circular table of diameter 1m. The ratio of illuminaces at the centre and the edge is
[NCERT 1982]
Options:
A) $ \frac{1}{2} $
B) $ {{( \frac{5}{4} )}^{\frac{3}{2}}} $
C) $ \frac{4}{3} $
D) $ \frac{4}{5} $
Show Answer
Answer:
Correct Answer: B
Solution:
$ \frac{I _{centre}}{I _{edge}}=\frac{{{(r^{2}+h^{2})}^{3/2}}}{h^{3}} $
$ =\frac{{{( 1+\frac{1}{4} )}^{3/2}}}{1^{3}} $
$ ={{( \frac{5}{4} )}^{3/2}} $
