An astronomical telescope has an angular magnification of magnitude 5 for an object. The separation between the objective and the eye-piece is 36 cm . The final image is formed at infinity. The focal length f 0 of the objective and f e of the eye-piece are

Question

An astronomical telescope has an angular magnification of magnitude 5 for an object. The separation between the objective and the eye-piece is 36 cm . The final image is formed at infinity. The focal length f 0 of the objective and f e of the eye-piece are, 45 cm and - 9 cm, 50 cm and 10 cm, 72 cm and 2 cm, 30 cm and 6 cm

MARKS App · Accepted Answer

Magnification, m = - 5 = - f 0 f e ⇒ f 0 = 5 f e ⇒ L = f 0 + f e = 36 ⇒ 6 f e = 36 ∴ f e = 6 cm ⇒ f 0 = 5 f e = 30 cm

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