One of the most famous experiments about light involves passing it through slits and watching the light waves diffract or dissapate after the slit.
If two slits are used, a familiar pattern of interference occurs, as illustrated below.
A doctor Young early in the 1800s discovered this phenomenon. It follows the rule below:
m*λ = d * sinθ
Use the interactive applet below to experiment with a virtual dual slit experiment. You need to have Java Applets enabled on your web browser for the applet to display properly.