Diffraction of Light

Return to Basics of Light Menu

Light can be diffracted Diffraction effects occur when waves interact with objects having a size similar to the wavelength of radiation. Diffraction is not an important for optical fibers because there must be some specific order in the materials in order to have a diffraction pattern. When light goes through a slit there are two regimes that have been explored; close to the object as in Fresnel diffraction, and the effects of diffraction far from the object: Fraunhofer diffraction.

The result of diffraction is a set of bright and dark fringes, due to constructive and destructive wave interference, called a diffraction pattern.

The width of the light and dark lines is depends on the width of the slit and the wavelength of the light.

The intensity observed far from the slit is given by:

<math>I = I_0 (\frac {sin\lambda} {\lambda} sinx/x)^2\,\!</math>

where Where

<math>x = w \; sin(\frac {\theta}{\lambda})\,\!</math>

minima are found for %theta; values such that:

<math>Sin \theta_min = j\;\frac {\lambda} {w}\,\!</math>

with j = ±1, ±2, ±3, …

Therefore: the narrower the slit, the wider the fringe spacing