PURPOSE: To show that a sunspot appears as a dark spot on the sun's surface, but still radiates intense energy.
DESCRIPTION: A clear, unfrosted light bulb is laid on the overhead and the filament is viewed on the overhead screen, as shown in the above left photo. With the overhead lamp off, the clear filament is turned on and focused onto the overhead screen, as shown in the middle photo. The filament brightness is adjusted with a variac to be about 70% of full power. With the room lights of the filament is viewed by the class on the overhead screen.
Turn on the overhead lamp, as shown in the above right photo. Although the filament is still on, it is washed out and appears dark against the bright light of the overhead.
EQUIPMENT: Lamp, variac, wood riser, base with rod and clamp as photographed.
SETUP NOTES: Five minutes to get the stuff and adjust the filament brightness.
Updated by Jun Qi in 3/20/2000