Abstract
A brief review of lighting technologies is presented. Unavoidable restrictions for incandescent light bulbs caused by the Planck distribution and properties of the human eye are illustrated. The efficiency and luminous efficacy of thermal radiation are calculated for various temperatures; the results clearly show the limitations for thermal radiators. The only way to overcome these limitations is using non-thermal radiators, such as fluorescent lamps and light-emitting diodes (LEDs). Unique advantages of LEDs undoubtedly made a revolution in this field. A crucial element of this progress is the blue LEDs (Nobel Prize 2014). Some experiments with a blue and a green LED are described: (i) the luminescence triggered in a green-yellow phosphor inside a white LED by the blue LED; (ii) radiant spectra and 'efficiency droop' in the LEDs; (iii) modulation of the blue LED up to 4 MHz; and (iv) the h/e ratio from the turn-on voltage of the green LED. The experiments are suitable for undergraduate laboratories and usable as classroom demonstrations.
Original language | English |
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Article number | 035024 |
Pages (from-to) | 1-11 |
Number of pages | 11 |
Journal | European Journal of Physics |
Volume | 36 |
Issue number | 3 |
DOIs | |
State | Published - 1 May 2015 |
Bibliographical note
Publisher Copyright:© 2015 IOP Publishing Ltd.
Keywords
- Efficacy
- Efficiency
- LED
- Lighting
- Nobel prize