How is light produced in an LED light?

Answer 1

An LED produces light when current flows through it. The LED will have a rated current specified by the manufacturer. The current can be 2 mA for some of the smaller ones, 150 mA for the ones in most LED flashlights, up to 500 mA for some of the elements in LED traffic lights.

Some background: In order to conduct current, there must be at least a certain voltage across the LED. This is its "forward voltage." Evendiodes that don't emit visible light have the same requirement for a forward voltage before they conduct. Neither type of diode will conduct much current (or emit light) below that voltage, or if the voltage is reversed. Typical values for LEDs are 2V for red, 2.6V for green and 3.5V for white.

Too much reverse voltage across, or too much forward current through, a diode will damage it.

A very common method of lighting an LED is to connect a resistor in series and connect a voltage source, such as a battery, across them. The resistor helps limit the current through the diode and minimize the effect of variations in supply voltage and LED specification variability.

Some other notes:

Driving multiple LEDs in parallel from a single voltage source requires a resistor in series with each LED to compensate for the variations in forward voltage among LEDs.

Pulse width modulation (PWM) can be used to vary the brightness of an LED.

Answer 2

The application of an electric charge to the LED causes the electrons of the applied charge to excite the atoms in a semi-conductive material within the LED that then produces photons in the wavelength of visible light.

LEDs are more efficient than traditional light bulbs as they produce far less heat.

Traditional bulbs contain an element that heats up when a current is passed through it, becoming incandescent. This is terribly inefficient as light is essentially a by-product of the heated element, and much of the energy is wasted. In an LED, however, light is the primary radiated energy, and the transparent materials in the LED's construction allow that light to escape with very little being absorbed and lost as heat.

Answer 3

An LED is a semiconductor diode. It consists of a chip of semiconducting material treated to create a structure called a p-n (positive-negative) junction. When connected to a power source, current flows from the p-side or anode to the n-side, or cathode, but not in the reverse direction. Charge-carriers (electrons and electron holes) flow into the junction from electrodes. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon (light).

Answer 4

A red LED, for example, has inside it a P-N junction of Gallium Nitride (a semiconductor). When a current is passed through this, electrons in the junction are excited and diffuse from the N-type into the P-type. As they "jump the gap" they release a photon, this is where light is emitted.

Answer 5

A light-emitting diode (LED) is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting. Introduced as a practical electronic component in 1962, early LEDs emitted low-intensity red light, but modern versions are available across the visible, ultraviolet, and infrared wavelengths, with very high brightness.

When a light-emitting diode is forward-biased (switched on), electrons are able to recombine with electron holes within the device, releasing energy in the form of photons. This effect is called electroluminescence and the color of the light (corresponding to the energy of the photon) is determined by the energy gap of the semiconductor. LEDs are often small in area (less than 1 mm2), and integrated optical components may be used to shape its radiation pattern. LEDs present many advantages over incandescent light sources including lower energy consumption, longer lifetime, improved robustness, smaller size, and faster switching. LEDs powerful enough for room lighting are relatively expensive and require more precise current and heat management than compact fluorescent lamp sources of comparable output.

Light-emitting diodes are used in applications as diverse as aviation lighting, automotive lighting, advertising, general lighting, and traffic signals. LEDs have allowed new text, video displays, and sensors to be developed, while their high switching rates are also useful in advanced communications technology. Infrared LEDs are also used in the remote control units of many commercial products including televisions, DVD players, and other domestic appliances.

Answer 6

The application of an electric charge to the LED causes the electrons of the applied charge to excite the atoms in the LED that then produce photons in the wavelength of visible light.