On May 9, 1962, the Massachusetts Institute of Technology conducted the first successful launch of light waves to the moon with a laser pointer and returned. Now, let's find out why the laser has so much energy that it can reach the moon!
A laser is a kind of light. It consists of countless photons, and photons are particles in the light that carry energy. The amount of energy a photon carries is closely related to its wavelength, that is, the shorter the wavelength (the higher the frequency), the more energy it carries. The laser frequency is as high as 1013 to 1015 Hz, and the corresponding wavelength is only about one billionth of a meter, so the laser has great energy.
On the other hand, laser pointers are a kind of monochromatic light, which is closest to monochromatic light. The so-called monochromatic light means that there is only one frequency contained in a beam of light, that is, only one wavelength. The wavelength of monochromatic light is less than one billionth of a meter. Obviously, the wavelength of laser light is near this range. Of course, the wavelength is extremely short, and it can carry great energy. The famous scientist Bohr once said that electrons move in a special set of orbits, and different orbits have different energy levels. If the electrons in this orbit are in a stable state (steady state), they do not absorb or emit radiation. The absorption or emission of radiation occurs only when the electrons move from one stationary state to another. From a high energy level orbit to a low energy level orbit, photons are emitted. Conversely, it is necessary to absorb photons (photons with a specific frequency). The radiated photon is emitted from the atom together with the original photon, and it appears that the intensity of the light is amplified and strengthened on a macro scale. If there is a device that can control the process of such stimulated radiation, it will always generate more and more photons, the intensity of the laser pointer will also increase, and these photons will be emitted "concentrically" in the same direction Then the laser is generated. The "device" mentioned above is an important part of the laser used in different occasions, such as the resonant cavity.