An air bubble in a glass slab (µ = 1.5) is 5 cm deep when

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An air bubble in a glass slab (µ = 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

1. 7.5 cm
2. 10.5 cm
3. 7 cm
4. 10 cm

Correct Option: B

1.5 =	Real depth (R₁)
	Apparent depth (5 cm)

R₁ = 1.5 × 5 = 7.5 cm

For opposite face , 1.5 =	R₂	⇒ R₂ = 3 cm
	2

∴ Thickness of the slab = R₁ + R₂
= 7.5 + 3 = 10.5 cm