Question

Brilliance of diamond is due to

• A. shape
• B. reflection
• C. cutting
• D. total internal reflection

Answer 1

Answer: (D)

total internal reflection

Answer 2

Diamonds shines due to the phenomena of total internal reflection. Whenever light travels from a denser to a rarer medium at an angle greater than the critical angle, it gets reflected back. The critical angle is inversely proportional to the refractive index of the medium. Since the refractive index of air is $1.00029$ and that of diamond is $2.42$, therefore the critical angle for diamond is very low (24°). Hence, all the light incident on its surface gets reflected due to total internal reflection.

Total internal reflection can only occur when:

• Light enters from a denser medium into a rarer medium.
• The angle of incidence of light is greater than the critical angle of the medium.