REFRACTION OF LIGTH

 Refraction of light

                                                         

 The bending of light in the second medium when light is transmitted from one medium to the other medium is defined as refraction of light.

Refraction is the property exhibited by the light particle when it is transmitted from one medium to another.

 when the light particle  passes through the second medium in points at the boundary which separates the two media and then it is transmitted into the second medium.

When the light enters into the second medium the velocity of the light is changed due to the change in density of the second medium and the bending of the light depends upon the nature of medium and hence the velocity of the light is changed.

 the refraction of light is observed in two cases

case1.

when the light is transmitted from rarer  medium which is having less density into the denser medium having high density, it bends towards the normal which is drawn perpendicular to the surface of the medium. 

The light was traveling in the first medium striking the boundary is known as incident light and the light which  parents in the second medium is known as refracted light.

In this case the angle of refraction is less than the angle of incidence the reason is the light bends towards the normal is the second medium.

case 2.

when the light is transmitted from denser medium into the rarer medium.

Light is transmitted from denser medium to rarer medium the light  bends away from the normal in in the second medium. 

 in this case the angle of refraction is greater than the angle of incidence since the light bends away from the normal.

 laws of refraction 

1 the incident light reflected light and the normal all  are in the same plane

2. the incident light and the reflected ray not in the same medium.

3. angle of incidence and angle of refraction not equal to each other,

 Dispersion of light

 Splitting of white light into seven colours is defined as Dispersion of light.

 Isaac Newton discovered that white light consists of seven colours which are from violet to read in the order 

 when white light passes through certain materials like a prism  it splits into seven colours which is known as Dispersion of light.

  Dispersion of light is observed  due the reason that the all the colours do not have same velocity and refractive index.

 when white light enters into the prism like material striking the the angle of refraction  depends upon the colour and hence white light splits into 7 colours.

 spectrum of white light

 when white light splits into seven colours the order of the colours is from  violet to red which is known as spectrum of white light.

 It is observed that the white light consists of minimum wavelength and the wavelength of red colour is maximum.

 The intensity of violet colour is much greater than that of the intensity of red colour. 

the light which is having minimum wavelength and that of the violet is known as ultraviolet light.

 the light which is having  more wavelength than that of the red colour is known as infrared light.

 the range of the wavelength which is from violet to Red which can be visible to the human eye is known as visible light  and the Spectrum is known as visible light spectrum.

 Total internal reflection of light.

This is the phenomenon which is observed when the light light is transmitted from denser medium to rarer medium and the reflected light is completely reflected in the first medium when the angle of incidence is greater than Critical Angle C.

 when the  light is transmitted from denser medium to rarer medium the refracted light bends away from the normal in the second medium. 

The angle of refraction is greater than that of the angle of incidence.

 By increasing the angle of incidence the angle of refraction is also increased.  It is observed that at an angle of incidence the angle of refraction is exactly 90 degrees.

 This angle of incidence where the angle of reflection is exactly  90° is defined as Critical Angle ‘C’. 

The value of angle depends upon the material of the medium.

 further increase in angle of incidence the angle of refraction is greater than  90° and then the reflected light is completely reflected into the first medium instead of  transmitting into the second medium.

                                

Applications of total internal reflection

1. There are some natural applications of total internal reflection in the formation of optical illusions Like mirages,  rainbow rainbow  and sparkling of diamonds.

2. In communication systems optical fibers work on the principle of total internal reflection only. 

 The communication signals are converted into optical signals and sent through the cables which are made of optical fibres.

 

3.The working of periscope is based on total internal reflection of light.

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