Q. A boy is trying to start a fire by focusing Sunlight on a piece of paper using an equiconvex lens of focal length 10 $cm$. The diameter of the Sun is $1.39 \times 10^{9}\ m$ and its means distance from the earth is $1.5 \times 10^{11}m$. What is the diameter of the Sun’s image on the paper
A) $6.5 \times 10^{- 5}m$
B) $12.4 \times 10^{- 4}m$
C) $9.2 \times 10^{- 4}m$
D) $6.5 \times 10^{- 4}m$
Explanation
(c) $d = \frac{D \times f}{r_{1}} = \frac{1.39 \times 10^{9} \times 10 \times 10^{- 2}}{1.5 \times 10^{11}}$
$= 9.26 \times 10^{- 4}m$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.