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What do you know about   terms refractive index and Refraction?
Definition of refractive index:
Refractive index can be defined as follows:
A demanding optical point for any transparent material called as refractive index.
Second definition of refractive index:
The ratio of the speed of light in a vacuum  to the speed of light in a transparent material is known as refractive index .
Symbol of refractive index:
Refractive index is always represented by a following symbol:
(n)

Value of refractive index:
Light all the time actions more leisurely in a material as compared to in a vacuum, so the value of  refractive index always remains greater than 1.0.
Even though light typically moves in straight lines through optical materials. Light bents when it goes through a  such surface at which place value of the refractive index changes. For example  when it passes from air into glass.
The quantity of bending depends on the refractive indexes of  two media and the angle at which the light strike  to the surface between them .
Bending of light:
Bending of light as it passes in the course of a rectangular piece of glass if light is coming from  one  medium having a minimum value of refractive index n (n1) as compared to other one with a higher n (n2) then light bents toward the normal. If the light travels from n2 to n1 it is bent away from the normal. In  an effect, the more a substance has ability to bend or refract light, the greater will be its refractive index value is said to be.
Snell's Law:

Snell's Law  helps us to determine the amount the light which  is bent and for the passage from air to glass it is given by following value: n1 sin θ1 = n2 sin θ2 .
Work of Dutch scientist, Christiaan Huygens:

In  year of 1678, another Dutch scientist, Christian Huygens arranged a mathematical link to explain the observation of snell and planned that the refractive index of a material is connected to the speed of light travels at which it travels through the substance. Huygens also  determined that the ratio of  relating the angles of paths of light in two materials having differing refractive indices should have equal value to the ratio of the velocity  at which light travels while  passing through each material. So he postulated, light would take a trip more slowly through materials having a greater refractive index.
Another statement of Dutch scientist, Christiaan Huygens:

Another statement of Christian Huygens  is that the velocity of light through a material is inversely proportional to its refractive index. Although this point has since been proved from experimental technique , it was not instantly clear to a common of seventeenth and eighteenth century investigators who did not have a reliable means to measure the velocity of light.

To these scientists, light appeared to pass at the same speed, in spite of of the material through which it  has passed. It was more 150 years after Huygens passed away that the speed of light was measured with as much as necessary accuracy.

Angle Of Incidence  And Angle Of Refraction:
At the upper surface, θ1 is called angle of incidence and θ2 the angle of refraction.
Tracing Of Path Of Light:
The way of rays of  light through a prism can be drawn within the implementation of Snell's Law at each of the two prism surfaces .(Air (n) air=1) Mirror Prism (n)  Refraction of light by a prism From Snell's Law and assuming n of the air = 1 n of the prism

Introduction to refraction:
What do you know about refraction?
Definition of refraction
Refraction is a physical phenomenon that occurs every time a wave, such as light or sound, travels from one medium (substance) to another in which its speed of propagation is different.
History of refraction:

In ancient times, man had observed this quite strange but clear fact.
Work of Greek astronomer:

In  early of  the first century (A.D.), the antique Greek astronomer and geographer whose name was  Ptolemy made a good attempt to explain from a mathematical point of view that  the amount of bending (or refraction) which was occurred, but his planned law was later determined to be defective.

Work of Dutch mathematician Willebrord Snell:

In the era of 1600s, a Dutch mathematician Willebrord Snell accomplished in developing the  law which defined a value related to the ratio of the incident and refracted angles, which has consequently been called as the bending power or refractive index of a substance.
Defectsof Dutch mathematician Willebrord Snell:

To his disenchantment Snell never discovered the reason for the  refraction effect.
Example of refraction :

The pencil in water appears to be bent because light rays coming from the pencil are abruptly bent at the air-water interface before reaching our eyes.

Refraction of light:
Refraction of light can be seen when it comes from water, and produce the phenomena of illusion which objects in water come into view to be both hazy and closer than they really are.