Metal ion lasers are gas lasers that generate deep ultraviolet wavelengths. Different molecules absorb different wavelengths of radiation. Infrared galaxies emit more energy in the infrared than at all other wavelengths combined. Light consists of electromagnetic radiation of different wavelengths. The energy emitted at shorter wavelengths increases more rapidly with temperature. It is able to react to different light intensities and different wavelengths. Most of the emission at infrared wavelengths originates from interstellar dust. Ranges of wavelengths and frequencies are only approximate. Light is composed of electromagnetic energy of different wavelengths. The range of wavelengths or frequencies for wave phenomena is called a spectrum. White light is a combination of lights of different wavelengths in the visible spectrum. Silica exhibits fairly good optical transmission over a wide range of wavelengths. There are also films sensitive to non-visible wavelengths of light, such as infrared. Recombination is more likely to occur at longer wavelengths of radiation. X-rays are much harder to collect and focus than electromagnetic radiation of longer wavelengths.