Jee Main 2024 29 01 2024 Shift 1 - Question10
Question 10
If a biconvex lens of material of refractive index 1.5 has focal length $20 cm$ in air, then its focal length when it is submerged in a medium of refractive index 1.6 is
(1) $-160 cm$
(2) $160 cm$
(3) $1.6 cm$
(4) $-16 cm$
Show Answer
Answer: (1)
Solution:
$\frac{1}{20}=(1.5-1)\left(\frac{2}{R}\right)$
$R=20 cm$
$\frac{1}{f^{\prime}}=\left(\frac{1.5}{1.6}-1\right)\left(\frac{2}{R}\right)$
$=\frac{-1}{16} \times \frac{2}{20}$
$f^{\prime}=-160 cm$
BETA
