Question

The ratio of the diameter of the sun to the distance between the earth and the sun is approximately $0.009$. The approximate diameter of the image of the sun formed by a concave spherical mirror of radius of curvature $0.4m$ is

• A. $4.5\times {10}^{-6}m$
• B. $4.0\times {10}^{-6}m$
• C. $3.6\times {10}^{-3}m$
• D. $1.8\times {10}^{-3}m$

Answer 1

The correct option is D $1.8\times {10}^{-3}m$

$\theta =\frac{D}{d_{SE}}=\frac{d}{f}$
$\Rightarrow d=\frac{D}{d_{SE}}\times f$
$d=0.009\times 0.2$
$=1.8\times {10}^{-3}m$