Total internal reflection: As we know that, when light ray travels from one medium to another changes its direction of path due to the change in optical density of the medium. When light ray travels from optically denser medium to the optically rarer medium then some of the light get reflected back in the same medium and remaining light get refracted in the second medium and such a phenomenon of light is called as internal reflector light. We know that, when a ray of light travels from denser medium to rarer medium then it gets bended away from the normal. If we increase the angle of incidence slowly then angle of refraction also get increased and at one stage the angle of refraction is 90° for some angle of incidence. And further if we increase the angle of incidence then there will be no refraction of light and the ray will be totally internally get reflected. Such phenomenon of reflection of light is called as total internal reflection of light. And the angle of incidence in denser medium for which the angle of refraction in rarer medium is 90°, that angle of incidence is called as critical angle. So, we define total internal reflection as, if the angle of incidence exceeds the critical angle, then the total light get internally reflected.
(i) For critical angle the value of corresponding angle of refraction is____
a) 180°
b) less than 90°
c) greater than 90°
d) 90°
(ii) What is mean by optically denser and optically rarer medium?
(iii) How total internal reflection of light would be possible in case of optical fibers?