• Young’s double slit experiment demonstrates how light waves produced an interference pattern
• The experiment is shown below

Young’s double-slit experiment arrangement

• When a monochromatic light source is placed behind a single slit, the light is diffracted producing two light sources at the double slits A and B
• Since both light sources originate from the same primary source, they are?coherent?and will therefore create an observable interference pattern
• Both diffracted light from the double slits create an interference pattern made up of bright and dark fringes
• The wavelength of the light can be calculated from the interference pattern and experiment set up. These are related using the double-slit equation

Double slit interference equation with a, x and D represented on a diagram

• The interference pattern on a screen will show as ‘fringes’ which are dark or bright bands
• Constructive?interference is shown through?bright?fringes with varying intensity (most intense in the middle)
• Destructive?interference is shown from?dark?fringes where no light is seen
• A monochromatic light source makes these fringes clearer and the distance between fringes is very small due to the short wavelength of visible light