### Properties of light

Light is electromagnetic radiation that has wave properties. Light waves can travel in a straight line. The light rays travel at the speed 3×108 or 186000 miles/sec. in free space. Light is a basic form of energy produced by the luminous object. It can travel through a vacuum. A light source needs characteristics of light must be possible to operate the device continuously at a variety of temperatures for many years.

Let us now check it out the primary definitions which we will be using while discussing optical fiber.

1. Refractive Index :

Refraction is the bending of a light ray that occurs when a light ray passes from one medium to another.

So it usually happens when the light to them from one medium to the next. The measure of how much light refract in a medium call index of refraction.

Refractive index can be defined as, n of an optical parameter of a material or substance as the ratio of the speed of light(c) in the air to the speed of light(v) in another medium, such as glass, water etc.

Where,

Refractive index  n = Speed of light in air (c) / speed of light in a material (glass-v)

n = Refractive index
c = Speed of light,  speed of light in free space = 3×108 or 186000 miles/sec
v = speed of light in a material

Now will discuss the index of refraction in a different material
• Air - 1.003
• Vacuum - 1
• Water - 1.33
• Glass fiber - 1.5-1.9
• Diamond - 2.0 - 2.42
• Silicon - 3.4
• Gallium arsenide - 2.6
Due to the refraction of light, we have to observe the various effect in our daily life. The following some example of them.
• A stick partially dipped in water seems to be sent
• A clear pool of water always appears to be shallower than compare it actually is.
2. Reflection :

The law of reflection state that when the light ray incident upon a reflective surface at some of the incident angle i from imaginary perpendicular normal, the ray will be reflected from the surface at some angle rfrom normal which is equal to the angle of incident.

The angle of reflection =  r = the angle at which the light is reflected from a surface is called the angle of reflection
i =  r

The angle of incidence  is the same as = the angle of reflection

The angle at which the light strikes a surface of the mirror with respect to the normal is called the "angle of incidence". The figure shows that the law of refraction and reflection.

3. Diffraction :

Diffraction is the slight bending of light as it passes around the edge of an object side. It refers to various phenomena that occur when a wave encounters an obstacle or silt. It is also defined as the bending of light around the corners of an obstacle or aperture into the region of the geometrical shadow of the obstacle. every cloud is a silver lining is the example of diffraction.

4. Dispersion :

The process on which light is separated into its colors due to the different degree of refraction, so the separation of visibility into its different colors is known as dispersion.