Question 1

What is Snell's Law?

Accepted Answer

Snell's Law (n₁ sinθ₁ = n₂ sinθ₂) describes the relationship between the angles of incidence and refraction when light crosses the boundary between two media with different refractive indices. When light enters a denser medium (higher n), it bends toward the normal. When it enters a less dense medium, it bends away from the normal.

Question 2

What is the refractive index?

Accepted Answer

The refractive index (n) of a material is the ratio of the speed of light in a vacuum to the speed of light in that material: n = c/v. Higher refractive index means light travels slower in that medium. Air has n ≈ 1.00, water n ≈ 1.33, glass n ≈ 1.52, and diamond n ≈ 2.42.

Question 3

What is total internal reflection?

Accepted Answer

Total internal reflection occurs when light traveling in a denser medium hits the boundary with a less dense medium at an angle greater than the critical angle. Instead of refracting through, all light is reflected back. This phenomenon is essential for fiber optics, prisms in binoculars, and the sparkle of diamonds.

Question 4

How is the critical angle calculated?

Accepted Answer

The critical angle θc = arcsin(n₂/n₁) exists only when n₁ > n₂ (light going from denser to less dense medium). For glass (n=1.52) to air (n=1.00), the critical angle is about 41.1°. For water to air, it is about 48.8°. At angles above the critical angle, total internal reflection occurs.

Snell's Law Calculator (n₁ sinθ₁ = n₂ sinθ₂)

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