why does a diamond sparkle
(Answer #1). The critical angle is the largest angle at which light rays inside a diamond can escape. The more a material bends light, the higher the RI Refractive index, the smaller its critical angle.Because diamond has a high RI, it has only a small critical angle, 24.5 degrees.Answer #1). The critical angle is the largest angle at which light rays inside a diamond can escape. The more a material bends light, the higher the RI Refractive index, the smaller its critical angle.