An astronomical refracting telescope is made from two lenses. The objective lens has a focal length of 114 cm, and the eyepiece lens has a focal length of 17.0 cm.
(a) What is the total length of the telescope?
(b) What is the angular magnification of the telescope?
(c) What is the magnification by turning the telescope around and looking through the objective
Lens first?
A) (a) $262 \mathrm {~cm}$
(b) $0.87$
(c) $1.15$
B) (a) $131 \mathrm {~cm}$
(b) $6.71$
(c) $0.15$
C) (a) $194 \mathrm {~cm}$
(b) $1.18$
(c) $0.85$
D) (a) $97 \mathrm {~cm}$
(b) $0.15$
(c) $6.71$

Question

An astronomical refracting telescope is made from two lenses. The objective lens has a focal length of 114 cm, and the eyepiece lens has a focal length of 17.0 cm.
(a) What is the total length of the telescope?
(b) What is the angular magnification of the telescope?
(c) What is the magnification by turning the telescope around and looking through the objective
Lens first? 
A) (a) $262 \mathrm {~cm}$
(b) $0.87$
(c) $1.15$
B) (a) $131 \mathrm {~cm}$
(b) $6.71$
(c) $0.15$
C) (a) $194 \mathrm {~cm}$
(b) $1.18$
(c) $0.85$
D) (a) $97 \mathrm {~cm}$
(b) $0.15$
(c) $6.71$

Quizplus · Accepted Answer

The total length of the telescope is the sum of the focal lengths of the objective and the eyepiece, which is $114 \mathrm{cm} + 17.0 \mathrm{cm} = 131 \mathrm{cm}$. The angular magnification of a telescope is given by the ratio of the focal length of the objective lens to that of the eyepiece lens, which is $114 \mathrm{cm} / 17.0 \mathrm{cm} = 6.71$. When the telescope is turned around, the magnification is the inverse of the original magnification, which is $1 / 6.71 = 0.15$.

An Astronomical Refracting Telescope Is Made from Two Lenses 262 cm262 \mathrm {~cm}262 cm

An Astronomical Refracting Telescope Is Made from Two Lenses $262 \mathrm {~cm}$