Question

The diameter of the sun is $1.4\times {10}^{9}m$ and its distance from the earth is $1.5\times {10}^{11}m.$ The radius of the image of the sun formed by a lens of focal length $20cm$ is

• A. $93mm$
• B. $0.093mm$
• C. $9.3mm$
• D. $0.93mm$

Answer 1

The correct option is D $0.93mm$

In this setup we can assume $u=\infty$

Hence image will be formed at focus.

Given, $v=20cm=0.2m$

$h_o=1.4\times {10}^{9}m$

$u=1.5\times {10}^{11}m$

$\therefore m=\frac{h_i}{h_o}=\frac{v}{u}$

$h_i=\frac{v{h}_o}{u}=\frac{0.2\times 1.4\times {10}^9}{1.5\times {10}^{11}}=\frac{1.86}{2}=0.93mm$

Hence the correct answer is option (D).