Optics Question 577
Question: A convex lens of focal length $ f $ is placed somewhere in between an object and a screen. The distance between the object and the screen is $ x $ . If the numerical value of the magnification produced by the lens is $ m, $ , then the focal length of the lens is
Options:
A) $ \frac{mx}{{{(m+1)}^{2}}} $
B) $ \frac{mx}{{{(m-1)}^{2}}} $
C) $ \frac{{{(m+1)}^{2}}}{m}x $
D) $ \frac{{{(m-1)}^{2}}}{m}x $
Show Answer
Answer:
Correct Answer: A
Solution:
$ \frac{v}{-u}=-mandv+u=x\Rightarrow u=\frac{x}{1+m} $
$ \frac{1}{f}=\frac{1}{v}-\frac{1}{u}\Rightarrow f=\frac{mx}{{{(m+1)}^{2}}} $ .
