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° at the objective the angular width of the image is

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° at the objective the angular width of the image is (A) 10°  (B) 24°  (C) 50°  (D) 48°

Tardigrade Admin · Accepted Answer

(f0/fe)=(β /α ) (60/5)=(β /2) β=24°

$1 0^{\circ}$

$2 4^{\circ}$

$5 0^{\circ}$

$4 8^{\circ}$

$\frac{f _{0}}{f _{e}} = \frac{β}{α}$
$\frac{60}{5} = \frac{β}{2}$
$β = 2 4^{\circ}$

Q. 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∘ at the objective the angular width of the image is

10∘

24∘

50∘

48∘

fe​f0​​=αβ​ 560​=2β​ β=24∘

$1 0^{\circ}$

$2 4^{\circ}$

$5 0^{\circ}$

$4 8^{\circ}$

$\frac{f _{0}}{f _{e}} = \frac{β}{α}$
$\frac{60}{5} = \frac{β}{2}$
$β = 2 4^{\circ}$