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# thickness of a slab

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An air bubble in a glass slab with refractive index 1.5 (near normal incidence) is 5 cm deep when viewed from one surface and 3 cm deep when viewed from the opposite face. The thickness (in cm) of the slab is

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@Krupa

As we learnt in

Relation between real depth and apparent depth -

$\frac{n_{i}}{d}= \frac{n_{r}}{d{}'}$

- wherein

$n_{i}$ = Refractive index of medium of incident.

$n_{r}$ = Refractive index of medium of refraction.

d = distance of object.

$d{}'$ = apparent  depth

Apparent depth = 5cm  from one side

$\therefore$ Real depth=1.5 $\times$ 5=7.5 cm

apparent depth = 3cm from other side

$\therefore$ Real depth from other side =3 $\times$ 1.5cm = 4.5 cm

$\therefore$ Thickness of slab = 7.5cm + 4.5cm = 12cm

12. An air bubble in a glass slab with refractive index 1.5 (near normal incidence) is 5 cm deep when viewed from one surface and Â 3 cm deepÂ

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