Refraction index, also called refractive index, a dimensionless number, of a material that describes how much the speed of light is reduced when it travels through that material compared with its speed in a vacuum. It also describes how much light bends, or changes direction, when it passes from one medium into another.
Refraction Index Formula |
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\( n \;=\; \dfrac{ c }{ v }\) (Refraction Index) \( c \;=\; n \cdot v \) \( v \;=\; \dfrac{ c }{ n }\) |
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| Symbol | English | Metric |
| \( n \) = Refraction Index | \(dimensionless\) | \(dimensionless\) |
| \( c \) = Speed of Light | \(ft\;/\;sec\) | \(m\;/\;s\) |
| \( v \) = Phase Velocity in a Specific Volume | \(ft\;/\;sec\) | \(m\;/\;s\) |
Because the speed of light in any transparent material is less than its speed in a vacuum, the refractive index of most materials is greater than 1. A vacuum has a refractive index of exactly 1. Air at standard conditions has a refractive index very close to 1.0003, water has a refractive index of approximately 1.333, and common glass typically has a refractive index between about 1.5 and 1.9, depending on its composition.
The refractive index determines how light changes direction when it crosses a boundary between two materials. This bending of light is called refraction. When light travels from a material with a lower refractive index into a material with a higher refractive index, it bends toward the normal line (an imaginary line perpendicular to the surface). When it travels from a higher refractive index material into a lower refractive index material, it bends away from the normal line.
Refractive Index Interpretation
