JEE PYQ: Ray Optics Question 27
Question 27 - 2020 (08 Jan Shift 1)
The magnifying power of a telescope with tube length 60 cm is 5. What is the focal length of its eye piece?
(1) 20 cm
(2) 40 cm
(3) 30 cm
(4) 10 cm
Show Answer
Answer: (4)
Solution
For telescope Tube length (L) $= f_o + f_e = 60$ and magnification ($m$) $= \frac{f_o}{f_e} = 5 \Rightarrow f_o = 5f_e$ $\therefore f_o = 50$ cm and $f_e = 10$ cm Hence focal length of eye-piece, $f_e = 10$ cm
BETA
