A parallel sided block of glass of refractive index `1.5`which is `36`mm thick rests on the floor of a tank which is filled with water (Refraction index=`4//3`).The difference between apparent depth of the floor at `A &B`when seen from vertically above is equal to

Options

A. `2mm`
B. `3mm`
C. `4mm`
D. noneof these

Answer

B

Explanation

shift through glass=`36(1-(1)/(3))=12mm`
shift through water =`36(1-(1)/(3))=9mm`
Difference =`3mm`
Difference of apparent depth of `A` and `B`=apprarent depth of `B`-appararent of depth of`A`
`(36)/(4//3)-(36)/(3//2)rArr` Difference of apparent depth of `A`and `B`=`27-24`
Difference of apparent depth of `A` and `B 3mm`