JEE PYQ: Ray Optics Question 37
Question 37 - 2019 (09 Apr Shift 2)
A convex lens of focal length 20 cm produces images of the same magnification 2 when an object is kept at two distances $x_1$ and $x_2$ ($x_1 > x_2$) from the lens. The ratio of $x_1$ and $x_2$ is:
(1) 2 : 1
(2) 3 : 1
(3) 5 : 3
(4) 4 : 3
Show Answer
Answer: (2)
Solution
Using, $M = \frac{v}{u}$ or $-2 = \frac{v_1}{x_1} \Rightarrow v_1 = -2x_1$ We have $\frac{1}{v} - \frac{1}{u} = \frac{1}{f}$ or $\frac{1}{-2x_1} - \frac{1}{x_1} = \frac{1}{20}$ $x_1 = 30$ cm And $\frac{1}{2x_2} - \frac{1}{x_2} = \frac{1}{20}$ or $x_2 = -10$ cm So, $\frac{x_1}{x_2} = \frac{30}{10} = 3$
BETA
