Non-ionizing radiation

[2][3] Non-ionizing radiation is used in various technologies, including radio broadcasting, telecommunications, medical imaging, and heat therapy.

The usual definitions have suggested that radiation with particle or photon energies less than 10 electronvolts (eV) be considered non-ionizing.

The light from the Sun that reaches the earth is largely composed of non-ionizing radiation, since the ionizing far-ultraviolet rays have been filtered out by the gases in the atmosphere, particularly oxygen.

This happens because at ultraviolet photon energies, molecules may become electronically excited or promoted to free-radical form, even without ionization taking place.

In such cases, even "non-ionizing radiation" is capable of causing thermal-ionization if it deposits enough heat to raise temperatures to ionization energies.

Much of the current debate is about relatively low levels of exposure to radio frequency (RF) radiation from mobile phones and base stations producing "non-thermal" effects.

Some experiments have suggested that there may be biological effects at non-thermal exposure levels, but the evidence for production of health hazard is contradictory and unproven.

Despite the possible hazards it is beneficial to humans in the right dosage, since Vitamin D is produced due to the biochemical effects of ultraviolet light.

In 2011, the International Agency for Research on Cancer (IARC) from the World Health Organization (WHO) released a statement adding RF electromagnetic fields (including microwave and millimetre waves) to their list of things which are possibly carcinogenic to humans.

[11] But a subsequent study reported that the basis of the IARC evaluation was not consistent with observed incidence trends.

For example, ultraviolet light, even in the non-ionizing range, can produce free radicals that induce cellular damage, and can be carcinogenic.

Ultraviolet light induces melanin production from melanocyte cells to cause sun tanning of skin.

Infrared (IR) light is electromagnetic radiation with a wavelength between 0.7 and 300 micrometers, which equates to a frequency range between approximately 1 and 430 THz.

This broad definition includes both UHF and EHF (millimeter waves), and various sources use different boundaries.

[7] In the related magnetosphere science, the lower frequency electromagnetic oscillations (pulsations occurring below ~3 Hz) are considered to be in the ULF range, which is thus also defined differently from the ITU Radio Bands.

Infrared radiation that one can feel emanating from a household heater, infra-red heat lamp, or kitchen oven are examples of thermal radiation, as is the IR and visible light emitted by a glowing incandescent light bulb (not hot enough to emit the blue high frequencies and therefore appearing yellowish; fluorescent lamps are not thermal and can appear bluer).

Theoretically a black body emits electromagnetic radiation over the entire spectrum from very low frequency radio waves to X-rays.