"Atomic theory of infrared night vision device
Atoms are in constant motion. They vibrate, move and spin constantly. Even the atoms that make up our seats are in constant motion. Atoms have several different excited states. In other words, they have different energies. If we give a large amount of energy to an atom, it will get out of the ground state energy level and reach the excited level. The excitation level depends on how much energy is applied to the atoms in the form of heat, light or electricity.
Atoms are made up of nuclei (including protons and neutrons) and clouds of electrons. We can imagine the electrons in the electron cloud moving around the nucleus in different orbits. It is not yet possible to observe the discrete orbitals of electrons, but it is easier to understand these orbitals by envisioning them as different energy levels of atoms. In other words, if we apply a certain amount of thermal energy to an atom, it is predictable that some electrons in low-energy orbitals will transfer to high-energy orbitals, i.e., farther from the nucleus.
After the electron is transferred to the high-energy orbit, it still has to return to the ground state eventually. During this process, electrons release energy in the form of photons, a type of light particle. You will find that atoms are constantly releasing energy in the form of photons. For example, when a heater in a toaster turns bright red, it's because atoms are thermally excited, emitting red photons. An electron in an excited state has a higher energy than an unexcited electron, and it is because the electron absorbs some energy to reach the excited level that it releases this energy to return to the ground state. This energy is released in the form of photons (light energy). The emitted photons have a specific wavelength (color), which depends on the energy of the electrons when the photons were emitted.
night vision goggles
night vision goggles
Any living thing consumes energy, as do many inanimate objects such as engines and rockets. Energy expenditure produces heat. Thermal energy, in turn, causes atoms in the object to emit photons that fall in the thermal infrared spectrum. The warmer the object, the shorter the wavelength of the infrared photons emitted. If an object is very hot, the photons it emits can even enter the visible light spectrum, starting with red light, then orange, yellow, white, and all the way to blue."
