Calculate the angle of refraction

Online calculator and formulas for calculating the optical angle of refraction


Use this calculator to calculate the optical angle of refraction or the angle of incidence.

To calculate, select whether you want to calculate the angle of refraction or the angle of incidence, enter the required values, and then click the "Calculate" button.


Refraction angle calculator

  What should be calculated?
input
Refractive index \(n_1 \)
Refractive index \(n_2 \)
Refraction angle \(θ_2 \)
Angle of incidence \(θ_1 \)
Decimal places
Result
  • \(n_1 \) - Refractive index of the first medium
  • \(n_2 \) - Refractive index of the second medium
  • \(θ_1 \) - Angle of incidence
  • \(θ_2 \) - Angle of refraction

Formulas for the angle of refraction and incidence


To calculate the angle of refraction, Snell's law of refraction is used. This law describes how light is refracted at the interface between two media. The formula is:

\[n_1· sin(θ_1)=n_2· sin(θ_2)\]

Where:

  • \(n_2 \) and \(n_2\) are the refractive indices of the two media
  • \(θ_1\) is the angle of incidence (measured to the normal of the interface)
  • \(θ_2\) is the angle of refraction

Rearrangement of the formula


Angle of refraction

\[n_1· sin(θ_1)=n_2· sin(θ_2)\]

\[ sin(θ_2)= \frac{n_1}{n_2} · sin(θ_1)\]

\[ θ_2 = arcsin\left(\frac{n_1}{n_2} · sin(θ_1)\right)\]

Angle of incidence

\[ θ_1 = arcsin\left(\frac{n_2}{n_1} · sin(θ_2)\right)\]


Example


In the example, it is assumed that light falls from air \(n_1= 1\) onto water \(n_2=1.33\) with an angle of incidence of 30°.

The angle of refraction is calculated as follows:

\[ sin(θ_2)= \frac{1}{1.33} · sin(30°)\]

\[ sin(θ_2)= \frac{1}{1.33} · 0.5≈0.3759\]

\[ θ_2= arcsin(0.3759)≈22.1°\]


Refractive indices for different materials


Material Refractive index (n)

Vacuum 1.00000
Air (at 0°C) 1.00029
Water (20°C) 1.3330
Ethanol 1.3614
Olive oil ~1.47
Benzene 1,501
Quartz glass 1,458
Window glass ~1.52
Plexiglass (PMMA) 1.49
Crown glass (BK7) 1.5168
Flint glass (heavy) ~1.6 - 1.9
Diamond 2,417

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