0
You visited us 0 times! Enjoying our articles? Unlock Full Access!
Question

A thin lens of refractive index 1.5 has a focal length 15 cm in air. When the lens is placed in a medium of refractive index 4/3, what is the new focal length?
  1. 60 cm
  2. 120 cm
  3. 70 cm
  4. 50 cm

A
60 cm
B
50 cm
C
120 cm
D
70 cm
Solution
Verified by Toppr

For the lens in air

1fa=(aμg1)[1R11R2]

115=(1.51)[1R11R2]

215=1R11R2

When the lens is immersed in water

1fw=(aμgaμw1)[1R11R2]

1fw=⎜ ⎜ ⎜1.5431⎟ ⎟ ⎟[1R11R2]

1fw[4.541][1R11R2]

1fw=18×215

1fw=160

fw=60cm.

Was this answer helpful?
17
Similar Questions
Q1
A thin lens of refractive index 1.5 has a focal length 15 cm in air. When the lens is placed in a medium of refractive index 4/3, what is the new focal length?
View Solution
Q2
A thin lens of refractive index 1.5 has a focal length of 15 cm in air. When the lens is placed in a medium of refractive index 4/3, its focal length will become

View Solution
Q3
A thin convex lens of refractive index 1.5 has 20cm focal length in air. If the lens is completely immersed in a liquid refractive index 1.6, its focal length will be :
View Solution
Q4
The focal length of a thin lens made from the material of refractive index 1.5 is 20cm When it is placed in a liquid of refractive index 4/3, its focal length will be ______ cm.
View Solution
Q5
A thin converging lens is made up of a glass of refractive index 1.5. It acts like a concave lens of focal length 50 cm when immersed in a liquid of refractive index (158) The focal length of the converging lens in air is (in m)
View Solution