Considering normal incident of ray, find equivalent refractive index of combination of two slabs shown in figure.

Options

A. `1.8`
B. `1.43`
C. 2
D. none of these

Explanation

(b) The equivalent refractive index of combination of slab for normal incidence is
`mu=(Sigma t_(l))/(Sigma (t_(l))/(mu_(l)))`
In this case` mu=(t_(1)+t_(2))/((t_(1))/(mu_(1))+(t_(2))/(mu_(2)))=(10+15)/(10/(4/3)+15/(3/2))`
`=25/(7.5+10)=25/(17.5=1.43`