How Can The Index Of Refraction For Lenses Be Measured?

Refraction is the bending of light as it passes from one medium to another. This bending is caused by the change is the speed of light in different media. As light enter an optically denser medium its speed decreases. For example, when light enters water from the air, its speed is reduced by approximately 23%.

Before going any further, it is important to understand the meaning of the following terms:

Incident Ray: It is the ray of light that strikes a surface.

Normal: A normal is a line perpendicular to that surface.

Refracted Ray: The ray of light that is transmitted through a surface is called a refracted ray. It always corresponds to a particular incident ray.

Angle of Incidence: The angle the incident ray makes with the normal.

Angle of Refraction: The angle the refracted ray makes with the normal.

The refractive index of a particular medium is the ratio of the speed of light in vacuum to the speed of light in that medium. It can be calculated as the sine of the angle of incidence divided by the sine of the angle of refraction. Therefore, the greater the refractive index of a particular medium, the greater will be the bending that would occur as light enters it.

The refractive index of a lens would be equal to the refractive index of the material it is made of. For glass, the refractive index ranges from 1.48 to 1.96.

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