Light goes from glass (n=1.5) to air (n=1.0) at 45°. What is the refraction angle?

You can work it out this way: apply Snell's Law: 1.5×sin(45°) = 1.0×sin(θ₂).

Find the critical angle for glass (n=1.5) to air.

Θ_c = arcsin(n₂/n₁) = arcsin(1/1.5).

Why does a diamond sparkle more than glass?

You can work it out this way: compare their indices of refraction and critical angles.

Pro 🔒~20 min

Bending Light

Explore refraction, reflection, and Snell's Law

How it works

Light bends when it crosses a boundary between materials with different indices of refraction. Snell's Law quantifies this: n₁sinθ₁ = n₂sinθ₂. When light travels from a denser medium to a less dense medium at an angle greater than the critical angle, total internal reflection occurs — the basis for fiber optics. The speed of light in a medium is c/n.

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Step-by-step

Adjust the incident angle and material indices.
The refracted beam updates in real time.
Find the critical angle by increasing the incident angle until the refracted beam disappears.
Measure angles using the protractor tool.

Key formulas

$n_1 \sin\theta_1 = n_2 \sin\theta_2$ Snell's Law
$\theta_c = \arcsin\left(\frac{n_2}{n_1}\right)$ Critical angle (TIR)
$n = \frac{c}{v}$ Index of refraction

Frequently asked questions

Light goes from glass (n=1.5) to air (n=1.0) at 45°. What is the refraction angle?: You can work it out this way: apply Snell's Law: 1.5×sin(45°) = 1.0×sin(θ₂).
Find the critical angle for glass (n=1.5) to air.: Θ_c = arcsin(n₂/n₁) = arcsin(1/1.5).
Why does a diamond sparkle more than glass?: You can work it out this way: compare their indices of refraction and critical angles.