6b40.10 Light bulb on a variac

PURPOSE: Demonstrate the change in the colors of the continuous spectrum as the brightness of the source changes.

DESCRIPTION:  The white light from slide projector passes through a slit and a prism to project a continuous spectrum on the OHP screen.  The power is of the lamp is changed by adjusting a variac. At low power the spectrum peak is shifted significantly to the red. At high power the spectrum peak is shifted toward the blue.

EQUIPMENT: Slide projector with a slit slide, variac and prism, as photographed.

SETUP TIME: 10 minutes.