A bubble in glass slab (µ = 1.5) when viewed from one side appears at 5 cm and 2 cm from otherside, then the thickness of the glass slab is:

10.5 cm

The correct answer is option 3: 10.5 cm

Given:

Refractive index of glass slab, $ \mu = 1.5 $

Apparent depth from one side = $5 \, cm$

Apparent depth from other side = $2 \, cm$

Let real depth of bubble from first side = $d$

Using relation: $ \text{Apparent depth} = \frac{\text{Real depth}}{\mu} $

$ 5 = \frac{d}{1.5} $

$ d = 5 \times 1.5 = 7.5 \, cm $

Let total thickness of slab = $t$

Distance of bubble from other side = $t - d$

Using same relation:

$ 2 = \frac{t - d}{1.5} $

$ t - d = 2 \times 1.5 = 3 $

$ t = d + 3 $

$ t = 7.5 + 3 = 10.5 \, cm $

Final Answer: Thickness of glass slab is $10.5 \, cm$