The students The students Understand the phenomena of total internal Understand the phenomena of total internal reflectionreflectionAppreciate the applications of total internal Appreciate the applications of total internal reflection in various fields reflection in various fields Develop logical reasoning abilityDevelop logical reasoning abilityAre Exposed to the use of Total Internal Are Exposed to the use of Total Internal Reflection in modern communication systemsReflection in modern communication systems

The students already knowThe students already know

• The phenomenon of Reflection and The phenomenon of Reflection and RefractionRefraction

• Laws of Reflection and RefractionLaws of Reflection and Refraction

What is Refraction?What is Refraction?

• Refraction is the bending of light at the surface of separation between two transparent media when light passes from one medium to another

• Light bends towards the normal when it travels from a rarer to denser medium

• Light bends away from the normal when it travels from a denser to rarer medium

Consider a ray of light travelling from a denser to rarer medium

The ray of light bends away from the normal in the rarer medium

Denser medium

Rarer medium

• The refracted ray bends more away from the normal and nears the surface of separation.

Now let’s increase the angle of incidence

Denser medium

Rarer medium

Now for a particular value of angle of incidence the refracted ray grazes the

surface of separationThis angle of incidence inside the denser medium, for which This angle of incidence inside the denser medium, for which

the refracted ray just grazes the surface of separation is the refracted ray just grazes the surface of separation is called the critical angle for the pair of media.called the critical angle for the pair of media.

What happens If the angle of incidence inside the denser medium

is greater than the critical angle?Then the ray is not refracted, But it is totally reflected internally obeying the laws of reflection. This phenomenon is called TOTAL INTERNAL REFLECTION

CONDITIONS FOR TOTAL INTERNAL REFLECTION

1.1. The light must travel from a denser to The light must travel from a denser to a rarer mediuma rarer medium

2.2. The angle of incidence must be The angle of incidence must be greater than the critical angle for the greater than the critical angle for the pair of media.pair of media.

APPLICATIONS OF TOTAL INTERNAL REFLECTION

• TOTAL REFLECTING PRISMS

• SPARKLING OF DIAMOND

• SHINING OF AIR BUBBLE IN WATER

• MIRAGE

• OPTICAL FIBRES

TOTAL REFLECTING PRISMS

• THEY ARE ISOCELES RIGHT ANGLED PRISMS

USES OF TOTAL REFLECTING PRISMS

• TO ROTATE A RAY OF LIGHT THROUGH 90

TO ROTATE A RAY OF LIGHT THROUGH 180

TO ERECT AN INVERTED IMAGE OR VICE VERSA

SPARKLING OF DIAMOND

SHINING OF AIR BUBBLES IN WATER

MIRAGEMIRAGE

OPTICAL FIBRES

ACKNOWLEDGEMENTS

NCERT Text Book for Class XII and http://www.ncert.nic.in for content