Question 1

What is Snell's Law?

Accepted Answer

Snell's Law describes how light bends when it passes from one medium to another: n₁ × sin(θ₁) = n₂ × sin(θ₂), where n₁ and n₂ are the refractive indices and θ₁ and θ₂ are the angles of incidence and refraction, measured from the normal to the interface.

Question 2

What is total internal reflection?

Accepted Answer

Total internal reflection (TIR) occurs when light travels from a denser medium (higher n) to a less dense medium (lower n) at an angle greater than the critical angle. At the critical angle, light refracts at exactly 90°. Beyond it, all light is reflected back — no refraction occurs. Fiber optic cables use TIR to transmit light.

Question 3

What is the critical angle?

Accepted Answer

The critical angle θc = arcsin(n₂/n₁) and only exists when n₁ > n₂. For example, light going from glass (n≈1.52) to air (n≈1.0003) has a critical angle of about 41°. Light hitting the interface at angles greater than 41° undergoes total internal reflection.

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