Refractive index of flint glass is 1.56 . Then the critical angle $$(I_c)$$ for glass air interface can also be expressed as $$Sin I_c$$ equals :

Correct option is A

The critical angle (Iₓ) for a given medium is the angle of incidence at which the angle of refraction becomes 90°. The formula to calculate the critical angle is:

sin Iₓ =$$\frac{1} {\text{refractive index of the medium}}$$​

For the glass-air interface,
Refractive index of flint glass = 1.56
Refractive index of air = 1 (approximately)

So,
sin Iₓ = $$\frac{1 }{ 1.56}$$​ = 0.64

Thus, the critical angle Iₓ for flint glass is approximately 0.64.

Information Booster

• Refractive index: It is a measure of how much a material bends light as it passes through. The higher the refractive index, the greater the bending of light.
• Critical angle: The critical angle is the minimum angle of incidence at which total internal reflection occurs when light passes from a denser medium to a less dense medium, like from glass to air.