Demonstrations

Planck's Constant - LED's

Code Number :	7A10.33
Disclaimer:	Reprinted by permission of Dick Berg, University of Maryland, for use on this website. The demonstrations contained and referenced herein are listed for the purposes of cataloging and describing physics demonstrations which should be conducted only under the direction of a trained instructional support professional or physicist. These demonstrations are not presented for the purpose of being conducted by persons unconnected to this Facility and/or persons not consulting with or being supervised by the recognized instructional support professional or physicist and his/her staff. The University is responsible only for those demonstrations carried out using its own equipment using established safety and scheduling policies, and bears no responsibility for those choosing to use this source material for their own purposes. All demonstrations described and contained herein are public domain, and can also be found in reference materials in libraries, bookstores, and electronic sources. Further information regarding legal liability in use of demonstrations and labs will be found on the web site Injuries in School/College Laboratories in USA. The University of Iowa Disclaimers: University of Iowa Disclaimer All Rights Reserved..
Condition :	Good
Principle :	Planck's Constant
Area of Study :	Modern Physics
Equipment :	LED array, oscilloscope, variac, 6 volt transformer, mulitmeter if desired.
Procedure :	The LED's are designed to be powered off of 6 volts. Use the multimeter to check the voltage if you wish. Hook the oscilloscope across the current resistor and the other lead across the diode. With an xy display a sharp "knee" in the curve is clearly seen. A plot of the "knee" voltage for the 6 different wave lengths of the array should give you measurements for Planck's Constant.

Web Sites

http://www.rose-hulman.edu/~moloney/AppComp/2001Entries/e07fr/eeqhfdemo.htm

References

Fred Inman, "A Simple Laboratory Experiment to Measure e/k", TPT, Vol. 43, # 1, Jan. 2005, p. 27.

Lawrence T. Escalada, N. Sanjay Rebello, and Dean A. Zollman, "Student Explorations of Quantum Effects in LEDs and Luminescent Devices", TPT, Vol. 42, # 2, Feb. 2004, p. 173.

Charles A. Sawicki, "Simple Uncertainty-Principle Experiment," TPT, p. 84 Vol. 41, # 2, (Feb. 2003).

"LED Correction", TPT, Vol. 35, # 4, Apr. 1997, p. 198.

D. F. Holcomb, "Apparatus for LED Measurement of Planck's Constant," TPT, Vol. 35, # 5, p. 261, (May, 1997).

D. F. Holcomb, "LED's: Their Charm and Pitfalls," TPT, Vol. 35, # 4, p. 198, (April, 1997).

L. Nieves, G. Spavieri, B. Fernandez, and R.A. Guevara, "Measuring the Planck Constant with LED's," TPT, Vol. 35, # 2, p. 108-109, (Feb., 1997).

David G. Fisher, "Diode Characteristics to Determine Boltzmann Constant," TPT, Vol. 30, # 5, p. 315, (May 1992).

John W. Jewett, "Get The LED Out", TPT, Vol. 29, # 8, Nov. 1991, p. 530.

Patrick J. O'Connor and Leah R. O'Connor, "Measuring Planck's Constant Using a Light Emitting Diode," TPT, Vol. 12, # 7, p. 423, (October 1974).

N. Sanjay Rebello, Chandramouli Ravipati, Dean A. Zollman, Lawrence T. Escalada, "Computer Simulation of p-n Junction Devices," AJP, 65, (8), August 1997, p. 765.

F. Herrmann, D. Schatzle, "Question #53, Measuring Planck's Constant by Means of an LED," AJP, 64, (12), Dec. 1996, p. 1448.

Robert Morehouse, "Answer to Question #53, Measuring Planck's Constant by Mean of an LED," AJP, 66, (1), Jan. 1998, p. 12.

David A. Johnson, "Demonstrating the Light-Emitting Diode," AJP, 63, (8), August 1995, p. 761.

D. Atkinson et. al. XXI International Physics Olympiad: Groningen, The Netherlands, 1990. Am. J. Phys., Vol. 60, No. 2, (February 1992).

S-100: "Light Emitting Diodes," DICK and RAE Physics Demo Notebook.

Charles Day, "Light-Emitting Diodes Reach the Far Ultraviolet," Physics Today, July 2006, p. 15.

Peter J. Mohr and Barry N. Taylor, "Adjusting the Values of the Fundamental Constants," Physics Today, pp. 29-34, (March 2001).

Jim Glenn, "One Very Small Number," Scientific Genius: The Twenty Greatest Minds, p. 129.

T. D. Rossing, C. J. Chiaverina, "6.8, Light-Emitting Diodes", Light Science, Physics and Visual Arts, p. 140.

Mail Questions and Comments to: Dale Stille