Question

A simple telescope consisting of an objective of focal length $60cm$ and a single eye-lens of focal length $5cm$ is focused on a distant object in such a way the parallel rays emerge from the eye lens. If the object makes an angle of $2^\circ $ at the objective the angular width of the image is

• A. $10^\circ $
• B. $24^\circ $
• C. $50^\circ $
• D. $48^\circ $

Answer 1

Answer: (B)

$\frac{f_{0}}{f_{e}}=\frac{\beta }{\alpha }$
$\frac{60}{5}=\frac{\beta }{2}$
$\beta=24^{\circ}$