Refraction, Glass Slab & Apparent Depth question from MHT CET 2025 (25 Apr, Shift 2)

Answer: (a)

1. If the bubble is $x$ from the first surface, its real distance from the opposite face is $21 - x$, and apparent distance $= \dfrac{21 - x}{\mu} = 6$.
2. With one data point, test the options: (a) $\dfrac{21 - 12}{1.5} = 6$ cm ✓.
3. Others fail: (b) $7/1.55 \approx 4.5$, (c) $10/1.6 = 6.25$, (d) $12/1.5 = 8$.
4. So the answer is (a) $1.5$, $12$ cm.