Snell's Law Calculator Formula

Understand the math behind the snell's law calculator. Each variable explained with a worked example.

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Formulas Used

Angle of Refraction

theta2 = asin(n1 * sin(theta1 * pi / 180) / n2) * 180 / pi

Variables

VariableDescriptionDefault
n1Refractive Index 11
theta1Angle of Incidence(°)30
n2Refractive Index 21.5

How It Works

Snell's Law

Snell's law describes how light bends when passing between media with different refractive indices.

Formula

n1 * sin(theta1) = n2 * sin(theta2)

Light bends toward the normal when entering a denser medium (higher n) and away from the normal when entering a less dense medium.

Worked Example

Light enters glass (n=1.5) from air (n=1) at 30 degrees.

n1 = 1theta1 = 30n2 = 1.5
  1. 01n1*sin(theta1) = n2*sin(theta2)
  2. 021*sin(30°) = 1.5*sin(theta2)
  3. 030.5 = 1.5*sin(theta2)
  4. 04sin(theta2) = 0.333
  5. 05theta2 = 19.47°

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