Refractive Index is the ratio between the speed of light in medium to speed in specific vacuum. When light travels in a medium, the atoms of that medium constantly absorb and re-emit the particles of light, which slows down the speed of light. The phenomenon of refraction deals with-
Speed of light as a medium depends on the properties of the medium.
Speed is dependent on the optical density of the medium in electromagnetic waves. Optical density has the tendency to restore the absorbed electromagnetic energy.
The more optically dense the material is, the slower the speed of light.
The refractive index is dimensionless. It is a number that indicates the number of times slower than a light wave would be in the material than it is in a vacuum.
The formula of the refractive index is as follows:
Here, n is the refractive index, c is the velocity of light in a vacuum and v is the velocity of light in a substance
The vacuum has a refractive index of 1.
The refractive index of materials can be calculated from the above equation.
Higher the refractive index is, the higher will be the optical density and slower is the speed of light.
Examples of Refractive Index
Refractive index of water is 1.33, which means the speed of light in the water is 1.33 times less than the speed of light in a vacuum.
Refractive index of glass is 1.52 and the refractive index of water is 1.33. The refractive index of glass is higher than the water, the speed of light in water is faster than the speed of light through glass.
When the refractive index of a medium is greater than that of another, then the first medium is said to be optically denser.
Refractive Index of Different Mediums
The Refractive Index of different mediums are-
Concave Mirrors and its Characteristics
When a mirror is cut into parts and the outer surface of the part is painted the mirror becomes a concave mirror. The characteristics of concave mirrors are-
When the concave mirror is placed close to an object, a magnified image is obtained.
If the distance between the object is increased the size of the image reduces and an inverted image is formed.
The image formed can either be small or large and can be virtual or real.
Convex Mirrors and its Characteristics
When the cut part of the hollow sphere is painted from inside,then the outer surface becomes reflecting. This kind of mirror is known as Convex Mirror. The Characteristics of convex mirrors are as follows-
The light diverges when it strikes the reflecting surface because of which it is also called a diverging mirror.
Erect, virtual and diminished images are formed with convex mirrors.