Question

15 Diamond has an index of refraction of 2.42, and part of the reason diamonds sparkle is that this encourages a light ray to undergo many total internal reflections before it emerges. (a) Cal culate the critical angle at which total internal reflection occurs in diamond. (b) Explain the interpretation of your result: Is it mea- sured from the normal, or from the surface? Is it a minimum angle for total internal reflection, or is it a maximum? How would the critical angle have been different for a substance such as glass or plastic, with a lower index of refraction?

Answer 1

Diamond has an indux refraction = 2.42 a) eta_2 sin theta_c = eta_1 sin n90 degree theta_c sin theta_c = 1/2 - eta_2 theta_c = sin^-1 (1/2-eta_2) theta_c = 24.4 degree (b) For total initial reflection light must goes from higher refractive medium in measured from normal. eta_2 sin theta_c = eta_1 sin 90 degree sin theta_c alpha 1/r_2 theta_c alpha 1/eta_2 rightarrow If eta_2 is lower the critical angle must be higher.