Light & Color

Interference Patterns

A laser shines through a variable slit pattern forming an interference pattern on a white screen two meters away. The slit pattern is mounted on a slide which the visitor can move up and down changing from a single slit to a double slit as well as changing the width of the single slit or the spacing of the two slits. The single slit diffraction pattern on the screen changes as the slit width changes. In fact the width of the diffraction pattern is inversely proportional to the size of the slit. The diffraction pattern of the double slit also varies its size in inverse proportion to the slit spacing. In addition, the diffraction pattern spreads out horizontally even though the slit is a vertical slit. This spreading is a result of the Heisenberg uncertainty principle.