<unk>  is energetic particles or waves that have the potential to ionize an atom or molecule through atomic interactions. It is a function of the energy of the individual particles or waves, and not a function of the number of particles or waves present.  A large flood of particles or waves will not cause ionization if the individual particles or waves are not energetic enough. These ionizations, if enough occur, can be destructive to biological organisms, and can cause DNA damage in individual cells.  Extensive doses of<unk>  have been shown to have a mutating effect to future generations of the individual receiving the dose. Examples of<unk>  are energetic Beta particles, neutrons, alpha particles and energetic photons (UV and above). The amount of energy required to ionize an atom or molecule may widely vary. X-rays and gamma rays will ionize almost any molecule or atom; Far ultraviolet, near ultraviolet and visible light are<unk>  to very few molecules; microwaves and radio waves are non-ionizing radiation.
Visible light is so ubiquitous that molecules that are ionized by it will often react nearly spontaneously unless protected by materials that block the visible spectrum. Examples include photographic film and some molecules involved in photosynthesis.<unk>  has many practical uses in medicine, research, construction, etc.  It also presents a health hazard to humans if used improperly. Both aspects are discussed below.
Ionizing radiation
Particle radiation
Irradiation
Carcinogen
Environmental radioactivity
Ultraviolet germicidal irradiation
Alkylating antineoplastic agent
Antitumorigenic herbs