Overhead projector, 200 watt light bulb on Variac
Light Bulb

 

Code Number: 8B10.50

Demo Title: Sunspots

Condition: Good

Principle: Temperatures of Gas and Plasma

Area of Study: Astronomy

Equipment: 

Overhead projector, 200 watt light bulb on Variac, VHS video tape of Sunspots on 11/01/90 from Van Allen rooftop.

Procedure:

Lay the light bulb on the overhead projector and focus so that a clear image of the filament is produced.  Turn off the overhead projector and turn up the Variac until the filament glows with a yellow to orange color.  Leave the Variac at that setting and turn on the overhead projector.  Since the light coming out of the overhead projector is produced by a hotter filament the filament image of the bulb will again appear dark or non-glowing (A Sun Spot).

References:

  • Sarah Lynn McGregor, Keith Goodale, "Don't Throw Away Your Old Overhead Projectors: Upcycle to Easy Physics Demos Instead", TPT, Vol. 63, #2, Feb. 2025, p. 107.
  • Thomas K. McCarthy, "A Doorway Can Be A Sunspot, Too!", TPT, Vol. 35, # 6, Sept. 1997, p. 334.
  • Thomas O. Callaway, Harry D. Downing, and Glen T. Clayton, "Classroom Demonstration of Sunspots", TPT, Vol. 20, # 3, Mar. 1982, p. 171.
  • Jay M. Pasachoff, Daniel B. Seaton, Kevin P. Reardon, "Sunspots and Their Cycle", Physics Today, Vol. 76, #2, Feb. 2023, p. 54.
  • Wallace A. Hilton, "G-9", Experiments in Optical Physics, p. 15.
  • "March 9, 1611: Dutch Astronomer Johannes Fabricius Observes Sunspots", APSNews, March 2015, Vol. 24, # 3, p. 3.
  • "Quiet Interlude in Solar Mass", AD Astra, Fall 2013, p. 55.
  • "Astronomy Demonstrations", PIRA News, Vol. 9, No. 3, p. 21, January 1995.
  • Carrina Storrs, "Solar Force Field", Popular Science, October 2009, p. 12.
  • H.J. Press,  "Image of the Sun",  Giant Book of Science Experiments, p. 11.
8B10.50 - Sunspots  - No Sound