A simple telescope consisting of an objective lens of focal length 60 cm and an eye lens of focal length 5 cm , is focused on a distant object. If the object subtends an angle of 2° at the objective lens, the angular width of the image is

Question

A simple telescope consisting of an objective lens of focal length 60 cm and an eye lens of focal length 5 cm , is focused on a distant object. If the object subtends an angle of 2° at the objective lens, the angular width of the image is (A) 50°  (B) ((1/6))°  (C) 10°  (D) 24°

Tardigrade Admin · Accepted Answer

Magnifying power for normal adjustment (distant object) is given by, M.P.=(β /α )=(fo/fe) ⇒ (β /2)=(60/5) ⇒ β =24°

Q. A simple telescope consisting of an objective lens of focal length $60 c m$ and an eye lens of focal length $5 c m$ , is focused on a distant object. If the object subtends an angle of $2^{\circ}$ at the objective lens, the angular width of the image is

$5 0^{\circ}$

$(\frac{1}{6})^{\circ}$

$1 0^{\circ}$

$2 4^{\circ}$

Magnifying power for normal adjustment (distant object) is given by,
$M . P . = \frac{β}{α} = \frac{f _{o}}{f _{e}}$
$\Rightarrow \frac{β}{2} = \frac{60}{5}$
$\Rightarrow β = 2 4^{\circ}$

Q. A simple telescope consisting of an objective lens of focal length 60cm and an eye lens of focal length 5cm , is focused on a distant object. If the object subtends an angle of 2∘ at the objective lens, the angular width of the image is

50∘

(61​)∘

10∘

24∘