Question

An air bubble in a glass slab (n = 1.5) is 5 cm deep when viewed from one face and 2 cm deep when viewed from the opposite face. The thickness of the slab is

• A. 10.5 cm
• B. 7.5 cm
• C. 7 cm
• D. 10 cm

Answer 1

Answer: (A)

10.5 cm

Answer 2

Refractive index $n=\frac{Real\, thickness}{Apparent\,thickness}$ or Real thickness = n $\times$ Apparent thickness $1.5 \times (5 +2) =1.5 \times 7 =10.5 cm$