Total internal reflection

Total Internal Reflection:
When a ray of light travelling in denser medium enters into a rarer medium,it bends away from the normal .if the angle of incidence 'i' increase,the angle of reflection 'r' also increases. For a particular value of angle of incidence,the angle becomes 90 degree. The angle of ,that causes the refracted ray in the rarer medium to bend through 90 degree is called Critical Angle.When the angle incidence becomes larger than the critical angle , no refraction occurs . The entire light is reflected back into the denser medium. This is known as Total Internal Reflection of light.