Question

Four lenses of focal length $+15cm,+20cm,+150cm$ and $+250cm$ are available for making an astronomical telescope. To produce the largest magnification, the focal length of the eyepiece should be

• A. $+15cm$
• B. $+20cm$
• C. $+150cm$
• D. $+250cm$

Answer 1

Answer: (A)

$+15cm$

In astronomical telescope, magnification is inversely proportional to focal length of eye piece. Hence, it will be minimum i.e. +15cm as in question.