Figure 1. A xenon halogen light bulb.
Halogen light bulbs are a fairly efficient light bulb that produce light from the flow of electricity. Halogen lights are used when filming but are also used in residential and commercial lighting, and in motor vehicles.
They are an advanced form of the incandescent light bulb; they work similarly yet last much longer:
- Higher pressures - the gas contained within the bulb is at a higher pressure (7-8 atm), making the bulb smaller than a normal incandescent. The bulbs must be made from stronger materials to maintain these pressures.
- Halogen gas - the gas inside of the halogen bulb combines with the tungsten vapor given off by the filament (the part that gets hot and emits light). If the temperature is high enough this vapor is redeposited on the filament, recycling the tungsten and extending the bulb lifetime.
The bulb is able gets much hotter, producing more light per unit of electricity compared to an incandescent bulb. A drawback is the severe burns halogen bulbs give when touched during operation.
- Small, lightweight, and easy to produce.
- A typical incandescent light may last up to 1000 hours, while a halogen light can last over 2500 hours.
- Halogen lights produce a color temperature closer to that of the Sun, which is more white in color compared to the orange color given off by incandescents. See the PhET simulation below for a comparison: incandescents operate at about 2800 K while halogens get up to 3400 K.
- Longer lifetime, as explained above.
- Instant startup (no need to warm up)
- Extremely hot (burn hazard).
- Could potentially explode due to high pressure, sending glass shards outward. This may be mitigated by a glass screen which acts as a shield to prevent injury.
The University of Colorado has graciously allowed us to use the following Phet simulation. Explore this simulation to see changing temperature changes the amount of radiation given by a light bulb filament. Note that much of the energy is coming off as heat (in the infrared spectrum, to the right of the visible spectrum):
For Further Reading