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The refractive index of a medium is 1.5. The speed of light in this medium is ________ m s⁻¹. [Speed of light in vacuum is c=3×10⁸ m s⁻¹]

Asked in GSEB Board March 2023 · Snell's law, slabs and apparent depth

Answer: (1) 2×10⁸

Step-by-step solution

Given: n=1.5 and c=3×10⁸ m s⁻¹.

Idea: the refractive index of a medium is defined as n=c/v, the factor by which the medium slows light down.

v=c/n=(3×10⁸)/(1.5)

v=2×10⁸ m s⁻¹

Light in ordinary glass travels at about two thirds of its vacuum speed, which is why a glass block delays a pulse and shifts an image.

Why the other options are wrong

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