An object is placed `20cm` in front of a block of glass `10cm` thick having its farther side silvered. The image is formed `23.2cm` behind the silvered face. The refractive index of glass is

Options

A. `1.41`
B. `1.46`
C. `1.51`
D. `1.61`

Answer

C

Explanation

Due to slab, mirror will be shifted towards object by
`10(1-1/mu)=10-(10)/(mu)=MM^'`
`OM^'=(20+10)-(10-(10)/(mu))=20+(10)/(mu)=M^'I`
`MM^'+MI=M^'I`
`10-(10)/(mu)+23.2=20+(10)/(mu)`
`(20)/(mu)=13.2impliesmu=(200)/(132)=1.51`