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Electromagnetic radiation and light

Light is a form of energy that can be transmitted from one object to another without any intermediate medium. This transmission of energy is called radiation. Radiation means that energy propagates in straight lines in all directions from a source, but in fact it does not always propagate in straight lines when passing through matter. It is known that some forms of radiation consist of particles, such as the radiation emitted by radioactive substances. Light was once thought to be a stream of particles, but later experiments proved that its properties were more properly explained as waves, and the direction of light was the direction of wave propagation. Less than a hundred years ago, it was proved that light waves are essentially electromagnetic waves, not matter like alpha particles emitted by radium or electrons. Later, it was found that light waves only account for a very small part of the extremely wide range of electromagnetic waves.

At the long-wave end of the electromagnetic spectrum are electromagnetic waves used for radio communication, with wavelengths ranging from tens of kilometers to a few millimeters; at the other end are x-rays and y-rays (gamma rays), which are emitted during nuclear reactions and have wavelengths even smaller than atoms. The visible part of the electromagnetic spectrum has a wavelength of about 380 to 760 nanometers (0.00038 to 0.00076 millimeters). The various wavelengths within this range can be distinguished by the color perception of the eye. Blue and purple are equivalent to short waves, red is equivalent to long waves, and yellow and green are in the middle of the visible wavelength range.

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