An equiconvec lens of glass `(mu_(g)-1.5)` of focal length `10cm` is silvered on one side. It will behave like a

Options

A. concave mirrorr of focal length `10 cm`
B. convex mirrorr of focal length `5.0 cm`
C. concave mirrorr of focal length `2.5 cm`
D. convex mirrorr of focal length `20 cm`

Answer

C

Explanation

For equiconvex lens
`|R_(1)|=|R_(2)|=f=10cm`
if `mu_(g)=1.5`
now `P=2P_(L)+P_(M)`
or`=(1)/(F)=2(mu-1)((1)/(R_(1))-(1)/(R_(2)))-(2)/(R_(2))`
`=2(1.5-1)((1)/(10)-(1)/(-10))-(2)/(-10)`
or `F=-2.5cm`
Therefore, the system will behave like a concave `m`