Question

State the laws of refraction. What is the meaning of “the refractive index of crown glass is 1.52”?

Answer 1

Hint: We have sometimes seen the light not reflect but can pass from one medium to another medium, which is known as refraction. It occurs only when a ray of light travels from one medium to another medium or (rarer to denser and denser to rarer) medium. For refraction, phenomenon existence can be known by its two laws. These two laws are called refraction of light.

Complete step by step answer:
The laws of refraction are:
(a) The incident ray, the normal ray, the refracted ray all lie in the same plane, i.e. they are coplanar.
(b) The ratio of the sine of the angle of incidence (i) to the sine of the angle of refraction(r) is constant for any two given media. The second law of refraction of light is also called Snell’s law.
$\therefore \;\dfrac{{{\mathop{\rm Sin}\nolimits} i}}{{{\mathop{\rm Sin}\nolimits} r}}\; = \;n$.

Here, n represents a refractive index .

Refractive index is defined as one medium with respect to others. Thus the refractive index of crown glass is 1.52 represents (refractive index of crown glass is 1.52 with respect to air). This shows that the speed of light in the crown glass will be 1.52 times slower in crown glass than in a vacuum.

Note: Refractive index has no unit; it is a dimensionless quantity. A medium having higher value of the refractive index is called optically denser medium, while the medium having a lower value of the refractive index is called optically rarer medium. It can be written as ${}^1{n_2}\; = \;\dfrac{{{{\rm{v}}_1}}}{{{{\rm{v}}_2}}}$ where v is called the speed of the medium.