Optics Question 437
Question: A telescope has an objective lens of focal length 200 cm and an eye piece with focal length 2 cm. If this telescope is used to see a 50 meter tall building at a distance of 2 km, what is the height of the image of the building formed by the objective lens
[AIIMS 2005]
Options:
A) 5 cm
B) 10 cm
C) 1 cm
D) 2 cm
Show Answer
Answer:
Correct Answer: A
Solution:
Magnification of objective lens $ m=\frac{I}{O}=\frac{v _{0}}{u _{0}}=\frac{f _{0}}{u _{0}} $
Therefore $ \frac{I}{50}=\frac{200\times {{10}^{-2}}}{2\times 10^{3}} $
Therefore I = 5 x 10^-2 m = 5 cm.
