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

Diameter of plano-convex lens is 6 cm and thickness at the centre is 3 mm. If speed of light in material of lens is 2×108m/s, the focal length of the lens is:
  1. 15 cm
  2. 10 cm
  3. 20 cm
  4. 30 cm

A
15 cm
B
30 cm
C
20 cm
D
10 cm
Solution
Verified by Toppr

The lens is as shown in the figure.

To determine the radius of curvature R of the curved surface, we can write

R2=32+(R310)2

Solving this, we get

R=15.15cm

Speed of light in any medium is cμ where c=3×108m/s and μ is the refractive index.

For the lens, cμ=2×108m/s

μ=3×1082×108=1.5

Putting these values in the lens makers formula for plano convex lens, we have,

1f=(μ1)(1R)=(1.51)(115.15)cm1

Solving this, we get f30cm

348045_31857_ans.png

Was this answer helpful?
15
Similar Questions
Q1
Diameter of plano-convex lens is 6 cm and thickness at the centre is 3 mm. If speed of light in material of lens is 2×108m/s, the focal length of the lens is:
View Solution
Q2
Diameter of plano – convex lens is 6cm and thickness at the centre is 3 mm. If speed of light in material of lens is 2×108 m/s, the focal length of the lens is:
View Solution
Q3
The diameter of aperture of a plano-convex lens is 6 cm and its maximum thickness is 3 mm. If the velocity of light in the material of the lens is 2×108m/s, its focal length is : (approximately)
View Solution
Q4
Diameter of a plano–convex lens is 6 cm and thickness at the centre is 3 mm. If the speed of light in the material of the lens is 2 108 m/sec, the focal length of the lens is
View Solution
Q5
The diameter of aperture of a plano-convex lens is 6 cm and maximum thickness is 3 mm. If velocity of light in material is 2×108 m/s, calculate focal length of the lens :
View Solution