The reason why light appears a certain color when it strikes a certain element is because electrons have energy levels which can be segregated by something called a “band gap”. the color of light is an indication of the energy level that its photons carry (measured in electron Volts or eV) as well as being directly correlated to its wavelength. When a material has a particular band gap the electrons in it absorb a specified amount of energy from the light and the rest of it is transmitted or reflected. You can predict what color an object will be, as well as if its crystalline form will be opaque or transparent based on its band gap classification. A laser beam works off of these principles. If it were not true, we wouldn’t have lasers.
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