- Arc Lamp Definition: An arc lamp is an electric lamp that creates light by forming an arc between two electrodes.
- Construction: Arc lamps have two electrodes in a glass tube filled with an inert gas.
- Working Principle: They work by ionizing the gas, creating an arc that emits light.
- Types and Colors: Different gases produce different light colors; for example, xenon gives white light, neon gives red, and mercury gives bluish light.
- Applications: Arc lamps are used in many areas, including outdoor lighting, searchlights, projectors, and medical equipment.
What is an Arc Lamp?
An arc lamp is defined as a type of electric lamp that produces light by creating an arc between two electrodes when electrical energy is supplied. Sir Humphry Davy invented the first arc lamp in the early 1800s using carbon electrodes. This arc was created in the air and was used in searchlights and high-intensity movie projectors.
Today, gas discharge lamps are widely used because they are more efficient than carbon arc lamps. They produce light by creating an arc, similar to carbon arc lamps, but they use an inert gas between the electrodes.
These lamps are enclosed in a glass tube under low pressure. The arc forms because the inert gas inside gets ionized. Examples include xenon, mercury, neon, krypton, and mercury-xenon arc lamps. Xenon arc lamps are the most widely used.
Working Principle of Arc Lamp
In a carbon arc lamp, the electrodes first touch in the air, causing a low voltage to create an arc. Then the electrodes are slowly separated, heating the electric current and maintaining the arc. This heating causes the carbon electrode tips to evaporate.
This carbon vapor produces a highly luminous, high-intensity light in the arc. The light’s color depends on temperature, time, and electrical characteristics.
In gas discharge lamps, the arc is produced in the space between the electrodes. Here, space is filled with an inert gas. The arc is produced by the ionization of this particular gas. The electrodes and the gas together are covered with a glass tube. When the electrodes are given high voltage power supply, the atoms in the gas experienced an inconceivable electric force and it results in the splitting of the atoms into free electrons and ions. Thus the ionizing of gas takes place (ionization process).
The broken atoms (free electrons and ions) move in contrasting directions. The two charges (free electrons and ions) collapse with each other and also with the electrodes. As a result, energy is emitted in the form of a flash of light. This flash of light is called an arc.
This is known as the formation of the arc and is done by the discharging process. So it is also known as discharge lamps. The name of the arc lamp and color of light emitted will directly depend on the atomic structure of the inert gas that is filled in the glass tube.
The typical temperature of an arc is over 3000°C or 5400°C. The color of the light emitted by the xenon arc lamp is white (similar to natural daylight) which is used widely. From the neon arc lamp, we get a red color and from the mercury arc lamp, bluish color is obtained. The combination of inert gasses is also used. They will give a more even light spectrum in a wider range of wavelengths.
Application of Arc Lamps
Arc lamps are commonly used in:
- Outdoor lighting
- Flashlights in cameras
- Floodlights
- Searchlights
- Microscope lighting (and other research applications)
- Therapeutics
- Blueprinting
- Projectors (including cinema projectors)
- Endoscopy
