Diffraction And Interference Investigation

 

Richard Feynman[4] said that

"no-one has ever been able to define the difference between interference and diffraction satisfactorily. It is just a question of usage, and there is no specific, important physical difference between them."

He suggested that when there are only a few sources, say two, we call it interference, as in Young's slits, but with a large number of sources, the process is labelled diffraction.

Commercial diffraction gratings consist of many closely spaced parallel grooves that will separate white light into component colors, just as a prism does.  A common example is the surface of a DVD. The image to the right illustrates the pattern of dots on the surfaces of a CD and DVD.  The width of a dot for the DVD is about 400 nanometers.

How does a diffraction grating cause the exhibition of a particular color?

A diffraction grating exhibits a periodic structure so light will interact with it in a specified and predictable manner.  Diffraction gratings can reflect a narrow range of wavelengths of light while allowing all others to pass through.  This results in a particular color being observed due to the reflection.