When the night comes, the lights give us light and warmth. We light them every day. But do you know how electric lights shine? Is there any change in it every day?
The light bulb is able to emit light because of the high heat generated by the current passing through the tungsten wire (also known as tungsten wire). We choose tungsten wire because it is the metal with the highest melting point (its melting point force is 3422 ℃), and it remains unchanged in the environment of more than 1000 ℃, while other metals have already melted away in this environment.
Tungsten wire, like many metals, is oxidized and burned out quickly at high temperature, so there is no oxygen in the bulb. But if all the air is pumped out to vacuum the bulb, the tungsten at high temperature can easily evaporate into gas, reducing the life of the bulb. What can I do?
In order to prolong the life of the bulb, the bulb will contain argon and inert gas, and add some pressure to reduce the chance of evaporation. In addition, iodine is added to the bulb to slow the evaporation of tungsten. This is because tungsten and iodine will change into tungsten iodide at about 1000 ℃, but when tungsten iodide contacts with high heat tungsten wire, it will change back to tungsten and iodine again. In this way, the life of the bulb can be prolonged a little.
The principle of fluorescent lamp is as follows:
The plasma discharge makes the low-pressure mercury vapor in the fluorescent lamp emit ultraviolet light with the wavelength of 254 nm, which is invisible to human eyes;
254 nm ultraviolet light excites the phosphor (halogen powder, i.e. calcium halide phosphate, chemical composition: Ca5 (PO4) 3CL: Sb, Mn), Sb (3 +) in the phosphor emits blue light, while Mn (2 +) emits yellow light. The blue light and yellow light are complementary colors and compound to form the white light we see. It can be seen from the principle that the whole process does not involve chemical reactions, so chemical changes cannot be counted.
