A bubble in glass slab \( (\mu = 1.5) \) when viewed from one side appears at 5 cm and 2 cm from other side, then the thickness of the glass slab is:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 10.5 cm
Viewed from outside, an object inside a slab appears nearer the surface, at the apparent depth. The real depth is the apparent depth multiplied by the refractive index of the slab.
\( \displaystyle \text{real depth} = \mu \times \text{apparent depth} \)
From the first side:
\( x_1 = 1.5 \times 5\,\mathrm{cm} = 7.5\,\mathrm{cm} \)
From the other side:
\( x_2 = 1.5 \times 2\,\mathrm{cm} = 3\,\mathrm{cm} \)
The bubble lies between the two faces, so the thickness is the sum of the two real depths.
\( t = x_1 + x_2 = 7.5\,\mathrm{cm} + 3\,\mathrm{cm} = 10.5\,\mathrm{cm} \)