CBSE Class 10 Science 2017 · Paper 531/1 · Question 5

Light - Reflection and Refraction 2 marks Easy

Write the relationship between absolute refractive index of a medium and the speed of light in vacuum. If the speed of light in vacuum is

3 \times 1 0^{8}

m/s, find the absolute refractive index of the medium in which light travels with a speed of

1.4 \times 1 0^{8}

m/s.

Answer

$n_{m} = \frac{c}{v}$ ; the absolute refractive index of the medium is about 2.14, with no unit.

The absolute refractive index of a medium is the speed of light in vacuum divided by the speed of light in the medium:

n_{m} = \frac{c}{v}

n_{m} = \frac{3 \times 1 0 ^{8} m/s}{1.4 \times 1 0 ^{8} m/s} = \frac{15}{7} \approx 2.14

(no unit).

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