Physical and Theoretical Chemistry

Photo Chemistry and Photo Biology

The study of how light impacts chemical reactions is known as photochemistry. This expression usually describes a chemical reaction that is triggered by the absorption of ultraviolet (wavelength from 100 to 400 nm), visible light (400-750 nm), or infrared energy (750–2500 nm). Photochemistry is essential to nature because it underpins photosynthesis, human vision, and the production of vitamin D in response to sunlight. Photochemical reactions operate differently from temperature-driven reactions. Photochemical pathways are able to swiftly overcome major activation barriers and enable reactions that would not otherwise be conceivable by accessing high energy intermediates that cannot be created thermally. Plastics' photodegradation serves as an illustration of the potential harm that photochemistry might cause.

The scientific study of the advantageous and detrimental effects of light (technically, non-ionizing radiation) on living things is known as photobiology. The study of photochemistry, photosynthesis, photomorphogenesis, visual processing, circadian rhythms, photomovement, bioluminescence, and the impacts of ultraviolet radiation are all included in this field. Typically, photon energies larger than 10 eV, which roughly correspond to both the first ionisation energy of oxygen and the ionisation energy of hydrogen at around 14 eV, are used to distinguish between ionising radiation and non-ionizing radiation.