PURPOSE: Very simple and clear demonstration of soap film
interference.
DESCRIPTION: A Bright source of light at the right illuminates a soap
film in the wire ring. The transmitted
light is seen at the left and the reflected light at the rear between the transmitted
light and the wire ring. Note that the reflected and transmitted colors are complements.
After a while the top section of the film becomes less than one-quarter wavelength thick,
so the waves reflected from the front and rear surfaces of the film are out of phase,
resulting in no reflected light .
EQUIPMENT: Soap film ring, as photographed.
SETUP TIME: 1/2 hour.
