Q. Find the luminous intensity of the sun if it produces the same illuminance on the earth as produced by a bulb of $10000\ candela$ at a distance $0.3\ m$. The distance between the sun and the earth is $1.5 \times 10^{11}m$
A) $25 \times 10^{22}cd$
B) $25 \times 10^{18}cd$
C) $25 \times 10^{26}cd$
D) $25 \times 10^{36}cd$
Explanation
(c) Illuminance produced by the sun $= \frac{L}{\left( 1.5 \times 10^{11} \right)^{2}}$
Illuminance produce by the bulb $= \frac{10000}{(0.3)^{2}}$
According to problem $\frac{L}{\left( 1.5 \times 10^{11} \right)^{2}} = \frac{10000}{(0.3)^{2}}$
$\Rightarrow L = \frac{2.25 \times 10^{22} \times 10^{4}}{9 \times 10^{- 2}} = 25 \times 10^{26}\ Cd$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.