Answer:
26.6°
Explanation:
refractive index of diamond, n = 2.23
When a ray of light passes from denser medium to the rarer medium and refracts at an angle of 90 degree from the normal of the surface, such angle of incidence in the denser medium is called the critical angle.
By the Snell's law
For critical angle, angle of incidence is critical angle, i = θc and angle of refraction, r = 90
So,
Sin θc / Sin 90 = 1 / 2.23
Sin θc = 0.448
θc = 26.6°
Thus, the critical angle is 26.6°.