define critical angle?write the relation between critical angle and refrective index?
Answers
Critical angle is the angle of incidence in the denser medium for which the angle of refraction in the rarer medium is 90°. Relation between Critical Angle and Refractive Index : The angle of incidence corresponding to an angle of refraction 90º, say ∠AON, is called the critical angle (ic) for the given pair of media. Using Snell’s law, if the relative refractive index is less than one then, since the maximum value of sin r is unity, there is an upper limit to the value of sin i for which the law can be satisfied, that is, i = ic such that sin ic = n21 The refractive index of denser medium 2 with respect to rarer medium 1 will be n12 = 1/sinic Red colour has maximum value of critical angle and Violet colour has minimum value of critical angle since,