Total Internal Reflection (TIR) - www.mywebpathshala.com

Total Internal Reflection (TIR)

Total Internal Reflection (TIR)

Total Internal Reflection (TIR)

The phenomenon in which a ray of light traveling from denser to rarer medium incident an angle greater than critical angle is totally reflected back to the same denser medium is called total internal reflection.

Critical angle (i_c) :

The angle of incidence in the denser medium for which angle of refraction in rarer medium is 90 degree is called critical angle.
It is denoted by i_c.

Necessary condition for total internal reflection:

Light must travel from denser to rarer medium.
The angle of incidence in the denser medium should be more than critical angle of that medium.

Relation between critical angle and refractive index:

from Snell’s law

${sin i}/ {sin r} = mu_1/mu_2$

here i = i_c , r = 90^0

so,

${sin i}/ {sin r} = {sin i_c}/ {sin 90^0} = mu_1/mu_2$

${sin i_c} = mu_1/mu_2$

if rarer medium is air mu_1 = 1 , mu_2 = mu

${sin i_c} = 1/mu$

$mu = 1/{sin i_c}$

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