Question

An astronomical telescope has an objective lens whose power is four diopter the lens is placed 30cm from the eye piece when the telescope is adjusted for minimum eye strain find the angular magnification of the telescope

Answer 1

Answer:

0.01.

Explanation:

Since, we get that in minimum adjustment of the lense from the eye the distance will be 25cm which will be image distance u. And the v is given in the question as 30 cm. So, the focal length of the eye piece will be 1/fe = 1/v - 1/u or 1/f = 1/(30) -1/(-25) which on solving we will get 1/f = 22/300 which on solving we will get 13cm approximately as the focal length of the eye piece.

So, the angular magnification will be focal length of objective/eye piece. Since, the objective 1/4 which is 0.25 cm. So, angular magnification is 0.25/13 which will be 0.01.

Answer 2

angular magnification of telescope is 5