Stimulated radiation, laser pointer: Einstein pointed out in theory in 1917. In addition to spontaneous emission, particles at high energy level E2 can also transition to lower energy levels in another way. He pointed out that when a photon with a frequency ν=(E2-E1)/h is incident, it will also cause particles with a certain probability. Rapidly transition from energy level E2 to energy level E1. Simultaneously radiating a photon with the same frequency, phase, polarization, and propagation direction as the external photon is called stimulated radiation. It can be imagined that if a large number of atoms are at the high energy level E2 when a photon with a frequency ν=(E2-E1)/h is incident, the atoms on E2 are excited to produce stimulated radiation, and two photons with the same characteristics are obtained. These two photons then excite the atoms at the E2 energy level, which in turn produce stimulated radiation. Four photons with the same characteristics can be obtained. This means that the original optical signal is amplified. The light generated and amplified during the stimulated radiation is laser light.
The laser pointer energy density is extremely high. The photon energy is calculated using E=hv. Where h is the Planck constant and v is the frequency. It can be seen that the higher the frequency, the higher the energy. The laser frequency range is 3.846×10^(14) Hz to 7.895×10^(14) Hz. The electromagnetic spectrum can be roughly divided into radio waves-wavelengths from several kilometers to 0.3 meters, the general TV and radio broadcasting bands use this wave; microwave-wavelengths from 0.3 meters to 10^-3 meters, these Wave is used in radar or other communication systems; infrared rays-wavelengths from 10^-3 meters to 7.8 x 10^-7 meters; visible light-this is a very narrow band that people can receive light. The wavelength is from 780-380nm. Light is an electromagnetic wave emitted when the motion state of electrons in atoms or molecules changes. Because it is the part of the electromagnetic wave that we can feel directly and feel very little; ultraviolet ray-the the wavelength is from 3×10^-7 meters to 6×10^-10 meters. The causes of these waves are similar to light waves and are often emitted during discharge. Because its energy is comparable to the energy involved in general chemical reactions, the chemical effect of ultraviolet light is the strongest; Roentgen ray-this part of the electromagnetic spectrum, the wavelength is from 2×10^-9 meters to 6×10^-12 meters. Roentgen ray (X-ray) is emitted when the inner electron of an electric atom jumps from one energy state to another or when the electron decelerates in the nuclear electric field. Gamma rays are electromagnetic waves with wavelengths ranging from 10^-10 to 10^-14 meters. This invisible electromagnetic wave is emitted from the nucleus. This radiation is often accompanied by radioactive material or nuclear reactions. Gamma rays have strong penetrating power and are very destructive to living things.