Low pressure gas discharge lamps are considered thermal sources because they produce light through the heating and excitation of gas molecules. The gas inside the lamp is heated to high temperatures, causing it to emit light in the form of photons. This process is similar to how thermal sources such as incandescent light bulbs and fire emit light.
The gas inside a low pressure gas discharge lamp is heated through the application of an electric current. This current is passed through the gas, causing collisions between the gas molecules and electrons. These collisions result in the transfer of energy to the gas molecules, increasing their temperature and causing them to emit light.
No, not all types of low pressure gas discharge lamps are thermal sources. Some types, such as fluorescent lamps, use a combination of gas discharge and phosphor coatings to produce light. In these lamps, the gas discharge is used to excite the phosphors, which then emit light. However, other low pressure gas discharge lamps, such as neon lights, rely solely on the heating and excitation of gas molecules to produce light.
One advantage of using low pressure gas discharge lamps as thermal sources is their high energy efficiency. They convert a large portion of the electrical energy into light, making them more efficient than incandescent bulbs. They also have a longer lifespan and produce less heat, making them safer to use. Additionally, they can produce a wide range of colors depending on the type of gas used.
One limitation of using low pressure gas discharge lamps as thermal sources is that they require a high voltage to start the gas discharge. This can make them more expensive to operate and can also lead to flickering or a delay in the lamp turning on. Additionally, the gas inside the lamp can become depleted over time, causing a decrease in light output and eventually requiring replacement of the entire lamp.