What is Refractive Index? Detailed Explanation with Examples

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Concept We know that the speed of light is maximum in a vacuum, which is (3 x 10^8 ) m/s.

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When light travels from air to any other medium, its speed decreases. In other words, it slows down.

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The medium in which the speed of light is less is called the optically denser medium.

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The medium in which the speed of light is more is called an optically rarer medium.

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The speed of light in glass is (2x10^8) m/s, and the speed of light in water is (2.25 x10^8)m/s.

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- So the glass is optically denser than water. - Both glass and water are optically denser than air.

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A beam of light travels in a straight path as long as it travels in the same medium, but it bends when it travels from one medium to another when it obliquely strikes the second medium.

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This bending ability of light in different media is termed a refractive index.

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Now we are in a position to define the refractive index of medium1 with respect to medium2.

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The refractive index of medium2 with respect to medium1 is the ratio of the speed of light in medium1 to the speed of light in the medium.

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Note that light enters from medium1 to medium2; the light gets refracted at the boundary of the two media.

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