Red/green/blue line source viewed with double slit paddles.

Young's Double Slit Experiment: A light bulb with a long straight filament resides behind a red, a green and a blue colored filter. This gives the effect that the top third is a glowing blue line of light, the middle third is a line of green light, and the bottom third is a line of red light. Wooden holders with 2 sets of double slits are passed out to the students. One set of double-slits is close together; the other set is spaced farther apart. By holding the mounted double-slit close to the eye and looking at the light source, a number of closely spaced interference fringes will be seen. It is noted that the blue fringes are closer together than the red fringes. Also, the fringes are spread farther apart looking through the set of slits that are closer together. The spacing between the fringes increases as the distance between the observer and the light source increases.