Optics Question 428
Question: A simple magnifying lens is used in such a way that an image is formed at 25 cm away from the eye. In order to have 10 times magnification, the focal length of the lens should be
[MP PET 1990]
Options:
A) 5 cm
B) 2 cm
C) 25 mm
D) 0.1 mm
Show Answer
Answer:
Correct Answer: C
Solution:
m = $ 1+\frac{D}{f _{e}} $
Therefore $ 10=1+\frac{25}{f _{e}} $
Therefore $ f _{e}=\frac{25}{9} $ $\tilde{}$ $ 25mm $
