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How to Calculate the Wavelength Change in a Material

Wavelength of a wave is the distance between its crests or troughs. Crests and troughs refer to wave's highest and lowest points. Different colors of light correspond to different wavelengths. When light enters a material, such as glass, its wavelength changes. The new wavelength depends on a quantity called refractive index of the material. Simply speaking, the refractive index of a material is a measure of the speed of light in that material.

Things You'll Need

Paper and pen
Refractive index of the material

Instructions

- 1
  Note down the wavelength of light before it enters the material -- that is, in free space or vacuum -- on a piece of paper. Call it L0. Let us assume that the wavelength is L0 = 470 nm, where nm stands for nanometer or a billionth of a meter.
- 2
  Find the refractive index of the material at L0 from a credible online source, such as the Filmetrics website. Let us assume that the material is glass and the refractive index at L0 for that glass is 1.5. Call this n and note it down on the paper.
- 3
  Divide L0 by n to find the wavelength in the material. For example, L = L0/n = 470/1.5 = 313.33 nm.
- 4
  Subtract L from L0 to find the change in wavelength. For example, the change is L0 - L = 470 - 313.33 = 156.67 nm.

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