A plano-convex lens having radius of curvature of first surface 2 cm exhibits focal length of in air. Another plano-convex lens with first surface radius of curvature 3 cm has focal length of when it is immersed in a liquid of refractive index 1.2. If b

STUDY MATERIALS
COURSES
MORE
SUCCESS STORY
ADMISSION
STORE

Back

JEE ADVANCE

CLASS XI - XII
CRASH COURSE

CLASS XI - XII

CRASH COURSE

JEE MAIN

CLASS XI - XII
CRASH COURSE

CLASS XI - XII

CRASH COURSE

NEET

CLASS XI - XII
CRASH COURSE

CLASS XI - XII

CRASH COURSE

BITSAT

CLASS XI - XII

CLASS XI - XII

CBSE BOARD

CLASS IX

CLASS X

CLASS XI

CLASS XII

CLASS VI

CLASS VII

CLASS VIII

UP BOARD

CLASS IX
CLASS X
CLASS XI
CLASS XII

CLASS IX

CLASS X

CLASS XI

CLASS XII

CUET

CRASH COURSE

CRASH COURSE

Courses

CLASSROOM COURSES
ONLINE COURSES

ONLINE COURSES

More

Solution

Q.
A plano-convex lens having radius of curvature of first surface 2 cm exhibits focal length of $f_{1}$ in air. Another plano-convex lens with first surface radius of curvature 3 cm has focal length of $f_{2}$ when it is immersed in a liquid of refractive index 1.2. If both the lenses are made of same glass of refractive index 1.5, the ratio of $f_{1}$ and $f_{2}$ will be: [2025]

1 3 : 5

2 1 : 3

3 1 : 2

4 2 : 3

Ans.
(2)

$\frac{1}{f_{1}} = (1.5 - 1) [\frac{1}{2} - 0] \Rightarrow f_{1} = 4 cm$

$\frac{1}{f_{2}} = (\frac{1.5}{1.2} - 1) (\frac{1}{3} - 0)$

$\frac{1}{f_{2}} = \frac{0.3}{1.2} \times \frac{1}{3} \Rightarrow f_{2} = 12 cm$

$\Rightarrow \frac{f_{1}}{f_{2}} = 4 : 12 = 1 : 3$

Want Us to Email you About Special Offers & Updates?