Question

An observer looks at a distant tree of height $10\, m$ 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.

Answer 2

Magnification of a telescope is given by:
$M =\frac{\theta_{ i }}{\theta_{ o }}$
$20=\frac{ h / d _{ i }}{ h / d _{ o }}$
$20=\frac{ d _{0}}{ d _{ i }}$
Distance of image, $d _{ i }=\frac{ d _{ o }}{20}$