what is refractive index and refraction?
Answers
Refraction
The change in direction or bending of a light wave passing from one transparent medium to another; caused by the change in wave’s speed is known as “Refraction”.
An example to understand this better is that of placing a straw/stick in a glass of water wherein it to be bent when viewed from any other angle than 900 to the surface. This happens because of bending of light rays as they move from air to glass. This bending of light depends on the speed of light in air and glass and the speed is dependent on the wavelength.
Refractive Index
The extent of bending of light rays entering from one medium to another is known as “Refractive Index”. It is denoted by the letter ‘n’. And can be represented as :
n = c/v
Where c = velocity/speed of light of a certain wavelength in the air and v = velocity of light in any medium.
The refractive index depends on:
a. nature of the medium
b. physical conditions
c. the color of the wavelength of light
The nature of a medium is defined as:
a. A medium is said to be “optically rarer” medium if the light in it travels faster.
b. A medium is said to be “optically denser” medium if the light in it travels slower.
If the value of the refractive index is high then, the bending effect light too will be higher. When passing from air into any medium. Any medium with a greater value of the refractive index (n) is an optically denser medium.
When we imagine a ray of light passing from air to any medium, say water; we draw a perpendicular to its surface known as the ‘normal’. Therefore when this ray of light passes from :
a. Optically denser medium to optically rarer medium it bends away from the normal.
b. Optically rarer medium to optically denser medium it bends towards the normal.
Hope helps