How is light emitted from incandescent lamps? Fluorescent lamps? Candles?
incandescent ... the filament is heated by the current flowing through it , causing it to glow ; like in a toaster oven
fluorescent ... the inside of the tube is coated with a material that fluoresces under ultraviolet light ... there is metal that is vaporized by the current through the tube ... the metal emits the UV light
candle ... heat from the oxidation (burning) of the wax , raises carbon atoms to higher energy states ; the atoms emit photons (light) as they return to a lower energy level
Light is emitted from different sources through different mechanisms. Here's how light is emitted from incandescent lamps, fluorescent lamps, and candles:
1. Incandescent Lamps:
Incandescent lamps produce light by heating a thin tungsten filament wire inside a bulb. When an electric current flows through the wire, it experiences resistance and gets heated to a high temperature. As the filament becomes hotter, it starts glowing and emits visible light. The tungsten filament also emits infrared radiation, which produces heat alongside the visible light. Incandescent lamps are not very efficient in converting electrical energy into light and are gradually being phased out due to their low energy efficiency.
2. Fluorescent Lamps:
Fluorescent lamps use a combination of gas and phosphor coatings to produce light. Inside the tube of a fluorescent lamp, there is a small amount of mercury vapor and a phosphor coating on the inner surface. When an electric current is applied, it ionizes the mercury vapor and generates ultraviolet (UV) light. The UV light strikes the phosphor coating, which absorbs the UV radiation and re-emits visible light. The phosphor coating determines the color temperature and intensity of the light. Fluorescent lamps are more energy-efficient than incandescent lamps but have drawbacks such as flickering and the presence of mercury.
3. Candles:
Candles produce light through a chemical reaction called combustion. They consist of a wick, typically made of cotton, surrounded by solid wax, such as paraffin or beeswax. When the wick is lit, heat is applied to the wax, causing it to melt. The heat vaporizes the liquid wax, which then combines with oxygen from the air and undergoes combustion. The combustion results in the release of heat, light, water vapor, and carbon dioxide. The light emitted by candles is primarily due to the incandescence of the tiny soot particles produced by incomplete combustion of the wax. The color and intensity of the light depend on the composition of the wax and the wick.
In summary, light is emitted from incandescent lamps through the heating and glowing of a tungsten filament, from fluorescent lamps through the excitation of mercury vapor and interaction with phosphor coatings, and from candles through the incandescence of soot particles produced by the combustion of wax.