Question

A telescope has an objective of focal length 100cm and an eye piece of focal length 2.5cmif you look into objective of this telescope you will see distant objects reduced in size. By what factor will angular size of objects be reduced

Answer 1

Magnification = focal length of eyepiece / least distance of distinct vision

m = 2.5/25

m=0.1

Answer 2

The angular size of objects in a telescope can be reduced by a factor of 40

Explanation:

Given : Objective focal length $(f_{o} )$ = 100 cm

Eyepiece focal length $(f_{e} )$ = 2.5 cm

To find: Factor by which angular size of objects is reduced.

Solution,

Angular width of image is 100cm

Angular wifth of object is 2.5cm

Magnification of telescope is given by

$m = \frac{f_{o} }{f_{e} }$

$m = \frac{100}{2.5}$

$m = \frac{1000}{25}$

m = 40

The magnification of telescope is 40

Final answer:

The angular size of objects can be reduced by a factor of 40

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