Question

The refractive index of glass is $1.5$. What is the meaning of this statement in relation to the speed of light?

Answer 1

The Refractive index is represented as a ratio of the speed of light in air to the speed of light in a medium. Since the refractive index is a fraction of two speeds, it is a dimensionless quantity. For the glass, possessing a refractive index of $1.5$, as stated in the question, means that the speed of light travels $1.5$ multiplies slower in that glass than in air.

Complete step by step solution:
The refractive index is described as the speed of light in vacuum divided by the light speed in medium.
$n = \dfrac{c}{v}$
n is a refractive index.
c is the light speed in vacuum.
v is the light speed in medium.
Put all the values in the above formula.
$c = 3 \times 10^{8} m s^{-1}$
$1.5 = \dfrac{3 \times 10^{8} }{v}$
$v = 2 \times 10^{8}$
The speed of light in a given medium i.e., glass is $2 \times 10^{8}$.
The speed of light in a given medium is $\dfrac{1}{1.5}$ times the speed of light in air.
The absolute refractive index denotes the refractive index of a medium in an emptiness. The refractive index of glass is $1.5$ means that the light speed in glass is $1.5$ times more delayed than the light speed in a vacuum. The light speed in glass depends on the color of light. The refractive index of a violet color component of white light is higher than the refractive index of a red color component.

Note: The refractive index of a medium is described as how the light moves through that medium. It is a dimensionless quantity. It explains how much a light ray can be turned when it begins from one medium to another. Snell’s law defines the relationship between the incidence angle and the refraction angle.