Light Emitting Diodes are electrical components that are used in a variety of applications to emit electromagnetic radiation by a process known as electroluminescence. The color that is emitted by the LED is dependent upon its frequency within the electromagnetic spectrum. Today there are a wide variety of frequencies that LED devices operate at.
Red LED Devices
Red LED devices operate at a wavelength of approximately 633 nm. The following equation can be used to determine the frequency of a LED device:
Frequency = speed of light / wavelength = (3 x 10^8) / (633 x 10^-9)
Carrying out this calculation leads to a frequency of 474 Terra-Hertz, which places it in the red region of the visible electromagnetic spectrum. Practical red LED devices were first invented in 1962 by Professor Nick Holonyak from the University of Illinois. Red LED devices are based upon the material indium gallium aluminum phosphide and are still used in a variety of technological industries.
Blue LED Devices
Blue LED devices were first invented by former Nichia scientist Shuji Nakamura in 1993. These devices operate at a wavelength of approximately 470 nm, therefore:
Frequency = speed of light / wavelength = (3 x 10^8 ) / (470 x 10^-9)
Completing the calculation leads to a frequency of approximately 638 Terra-Hertz. Modern blue LEDs are based upon the materials silicon carbide and gallium nitride, and are now cheap enough to be used in everyday electrical appliances.
Green LED Devices
Green LED devices were first realized in 2010 by scientists working at the National Renewable Energy Laboratory. These devices operate at a wavelength of approximately 560 nm and there have a frequency:
frequency = speed of light / wavelength = (3 x 10^8 ) / (560 x 10^-9)
Carrying out this calculation leads to a frequency of 535 Terra-Hertz. The final invention of green LED devices paved the way for the creation of white LED light sources.
White LED Devices
White light consists of individual red, blue and green components and hence does not consist of a single wavelength or frequency. White LED devices have a mixture of the frequencies 474 Terra-Hertz, 535 Terra-Hertz and 638 Terra-Hertz. The development of white LED devices has led to the possibility of cheap, energy efficient lighting that can be used in a variety of settings, from street lamps to desk lights.