Practice portal › Ray Optics and Optical Instruments › Refraction and Total Internal Reflection
Asked in GUJCET 2025 · Snell's law, slabs and apparent depth
Given: speed in the medium v = 200×10⁸ cm/s and c = 3×10⁸ m/s.
Idea: put both speeds in the same units before dividing. Since 1 cm = 10⁻² m, v = 200×10⁸×10⁻² = 2×10⁸ m/s.
The refractive index is n = c/v.
n = (3×10⁸)/(2×10⁸) = 1.5.
Skipping the centimetre-to-metre step would give n = 0.015, which is impossible: no medium carries light faster than vacuum, so n is never below 1.
So the refractive index of the medium is 1.5.
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