Question

# A plano convex lens when silvered in the plane side behaves like a concave mirror of focal length 30 cm. However, when silvered on the convex side it behaves like a concave mirror of focal length 10 cm. Then the refractive index of the material will be

A
3
No worries! We‘ve got your back. Try BYJU‘S free classes today!
B
2.0
No worries! We‘ve got your back. Try BYJU‘S free classes today!
C
2.5
No worries! We‘ve got your back. Try BYJU‘S free classes today!
D
1.5
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
Open in App
Solution

## The correct option is D 1.5Here, 1F=2f+1fm Plano-convex lens silvered on plane side will have focal length fm=∞. 1F=2f+1∞ ⇒f=60 cm Plano convex silvered on the plane side will have a focal length of R2. So, 1F=2f+2R⇒R=30 cm Now, from 1f=(μ−1)1R, we get μ=1.5

Suggest Corrections
2
Join BYJU'S Learning Program
Select...
Related Videos
Playing with Refractive Index
PHYSICS
Watch in App
Explore more
Join BYJU'S Learning Program
Select...