Question

Calculate the refractive index of glass, if the speed of light in glass is 2 x 10^8 m/s.

Answer 1

1.5 is the required answer.

GIVEN:

• Speed of light in glass, v = 2 × 10⁸ m/s

TO FIND:

Refractive index of the glass, μ

FORMULA:

μ = c/v

Where c is the velocity of light in free space or vacuum.

c = 3 × 10⁸ m/s

SOLUTION:

μ = c/v

$= \dfrac{3 \times {10}^{8} }{2 \times {10}^{8} } \\ \\ = \dfrac{3}{2} \times \dfrac{ {10}^{8} }{ {10}^{8} } \\ \\ = \dfrac{3}{2} \\ \\ = 1.5$

μ = 1.5

ANSWER:

Refractive index of the glass with respect to air is 1.5

REFRACTIVE INDEX:

• It is the ratio of two similar quantities. Hence it is unitless and dimensionless.

• According to snell's law, μ = sin i / sin r

• Absolute refractive index is always greater than one.

• Relative refractive index may be greater or equal to or less than one. It can be a fraction.

• Light travels faster in medium with lower refractive index.