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MHT CET 2026 (16 Apr, Shift 2) · Spherical Surfaces & Thin Lenses

Spherical Surfaces & Thin Lenses question from MHT CET 2026 (16 Apr, Shift 2)

Q14MHT CET 2026 · 16 APR · SHIFT 2Medium

Spherical Surfaces & Thin Lenses

A convex lens having refractive index 1.6 has focal length 12 cm, when it is in air. The focal length of that lens when placed in water is (refractive index of water = 1.28)

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Answer: (b)

$f_w = f_a \frac{\mu - 1}{\frac{\mu}{\mu_w} - 1}$
$\frac{1.6}{1.28} = 1.25$ , so $f_w = 12 \times \frac{0.6}{0.25} = 28.8$ cm
So the answer is (b) 288 mm.

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