Optics Question 486
Question: The maximum illumination on a screen at a distance of 2 m from a lamp is 25 lux. The value of total luminous flux emitted by the lamp is
[JIMPER 1997]
Options:
A) 1256 lumen
B) 1600 lumen
C) 100 candela
D) 400 lumen
Show Answer
Answer:
Correct Answer: A
Solution:
$ I=\frac{L}{r^{2}} $
$ \Rightarrow L=I.r^{2} $
$ =22\times 2^{2}=100 $ .
Now $ \varphi =4\pi L=4\times 3.14\times 100 $ = 1256 lumen.
