the magniuifying power of a telescope is 9. when it adjusted for parallel rays the didtance b/w the eye piece and  objective lens is 20cm find the focal length of both lenses

Asked by akgujrati04 | 22nd Aug, 2020, 07:06: PM

Expert Answer:

Let focal lengths of objective and eyepiece be fo and fe respectively. 
fo + fe = 20 ...(1)
Magnifying power of telescope is given as, 
fo/fe = 9 
Thus, 
fo = 9fe...(2)
Thus, 
9fe+fe = 20
10fe = 20
fe= 2 cm 
 
From eq(2), 
fo=9x2 = 18 cm 

Answered by Shiwani Sawant | 23rd Aug, 2020, 12:22: AM