Question

An observer looks at a distant tree of height $10m$ with a telescope of magnifying power of $20$. To the observer the tree appears:

• A. $10$ times taller
• B. $10$ times nearer
• C. $20$ times taller
• D. $20$ times nearer

Answer 1

Answer: (D)

$20$ times nearer

Magnification of a telescope is given by:

$M=\frac{{\theta }_i}{{\theta }_o}$

$20=\frac{h/d_i}{h/d_o}$

$20=\frac{d_o}{d_i}$

Distance of image, $d_i=\frac{d_o}{20}$