Question

Define ‘Refractive index of a transparent medium’. What is its unit? Which one has a higher refractive index, glass or water?

Answer 1

Hint The above problem is based on the concept of the refractive index. The refractive index is the ratio of the sine of the angle of incidence and sine of the angle of the refraction. It is the relative property of one medium with respect to another medium. The standard medium for the refractive index for all the material is air.

Complete step by step answer
When a ray of light moves from one medium to another medium then the light ray starts bending away or towards the normal at the boundary of both mediums. If the refractive index of another medium is higher than the incident medium then the light bends towards the normal otherwise away from normal. If the angle of incidence is more than the critical angle then light gets reflected in the incident medium without any refraction on another medium.
The medium in which the speed of light ray is more than other medium then the incident medium becomes rarer and another medium becomes denser medium. The refractive index is the same as either the ratio of speeds of light in both medium or ratio of sine of angles so the refractive index is dimensionless and it has no unit.
The speed of the light in the glass is less than the speed of the light in water, so the glass is denser medium than the water. The refractive index of the glass is higher than the refractive index of the water.

Note The absolute refractive index is given by the formula $n = \dfrac{c}{v}$ . Here c is the speed of the light in vacuum and v is the speed of the light in any medium. The refractive index of the air is assumed as 1 for other medium because the air is rarer medium compared to other medium.