Diffraction

From The Gemology Project
Revision as of 08:25, 11 March 2006 by Doos (talk | contribs) (Basic)
Jump to: navigation, search

Basic

In gemology diffraction is the bending of light waves around an obstacle or sharp edge. Either by transmission of light or reflection.

Diffraction of white light on a single slit


Colin Winter explaines it as water coming from a hose. It will travel in one direction. If you would hold your thumb partly over the opening, the water would get dispered in different directions.
Diffraction is also the dispersion of white light into its spectral colors (red, orange, yellow, green, blue, indigo and violet).

When dispersion happens on a prism, the violet part of the spectrum would get bended the most. In diffraction it is the red light that gets thrown away the furthest.
As the diffraction occurs in radiant waves, you will see a repetition of spectra along the center of the zero order prism (where none to little dispersion occurs).
The first order prisms (on both sides of the zero order) are the most clear ones and it is one of them that is used in diffraction grating spectroscopes.

Diffraction grating material is made up of thousands of small grooves (or rulings) that run parallel over the transparent material, acting as slits.
This causes diffraction to occur on all those grooves. Due to interference the different colors combine and the final result is seen as a spectrum of white light after transmission through the grating material.