There is an insect a cabin eying towards thick glass plate `P_(1)`, Insect sees the images of light source acrss the glass plate `P_(1)` outside tha chain. Cabin is made of thick glass plates of refractive index `mu = (3)/(2)` and thickness 3cm. Insect is eying from the middle of the cabin as shown in figure. (glass plates are partially reflective and consider only paraxial rays)

At what distance (from eye of insect) will the eye see the image ?

Options

A. `11 cm`
B. `14 cm`
C. `16.5 cm`
D. `18 cm`

Answer

D

Explanation

Second image will form due to reflection on left surface of `P_(1)`

For left surface of `P_(1)` light seems to coming from the distance `= (33)/(2)+3=(39)/(2)cm`
So, light seems to coming from `(45)/(2) cm` from right surfaces of `P_(1)`
So, final position of second image will be
`= (45)/(2)//(3)/(2)=15 cm`
So, distance of second image from insect `= 18 cm`.