Demonstrations of Frequency/Energy Relationships Using LEDs

• Graham T. Cheek ^[1]
  1. [1] United States Naval Academy

     United States Naval Academy

     Estados Unidos

     
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 92, Nº 6, 2015, págs. 1049-1052
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • The use of LEDs (light-emitting diodes) to demonstrate the relationship between frequency (or wavelength) and semiconductor energy level differences is described. LEDs can function as light detectors, and this ability is exploited to show the minimum light frequency needed to produce a voltage response in the LED. Light having higher energy (lower wavelength) than the detector LED bandgap energy produces a significant voltage response, whereas lower-energy light results in minimal response. The light sources can be other LEDs or a flashlight with colored filters. Alternatively, the voltage measured across an LED as it emits light under power can also be related to the LED bandgap energy, providing a somewhat more accurate estimate of the bandgap energy than that obtained from the LED detector mode. Although these demonstrations using LEDs are not technically the same as the classic photoelectric effect as presented in most freshman chemistry courses, they nevertheless illustrate the same relationships between frequency, wavelength, and energy level differences.