Ultraviolet radiationMacaneata Mihai MadalinPresuceanu Marian Stancu Cosmin Tomel

Generation

• The sun emits ultraviolet radiation in the UVA, UVB, and UVC bands. The Earth's ozone layer blocks 97–99% of this UV radiation from penetrating through the atmosphere.Of the ultraviolet radiation that reaches the Earth's surface, 98.7% is UVA. (UVC and more energetic radiation is responsible for the generation of the ozone layer, and formation of the ozone there). Extremely hot stars emit proportionally more UV radiation than the sun; the star R136a1 has a thermal energy of 4.57 eV, which falls in the near-UV range.

Detection

Ultraviolet radiations can be detected using devices like:• A photodiode is a type of photodetector capable

of converting light into either current or voltage, depending upon the mode of operation. The common, traditional solar cell used to generate electric solar power is a large area photodiode.

• Photomultiplier tubes (photomultipliers or PMTs for short), members of the class of vacuum tubes, and more specifically phototubes, are extremely sensitive detectors of light in the ultraviolet, visible, and near-infrared ranges of the electromagnetic spectrum. These detectors multiply the current produced by incident light by as much as 100 million times (i.e., 160 dB), in multiple dynode stages, enabling (for example) individual photons to be detected when the incident flux of light is very low.

Properties

• Ultraviolet radiation has wavelengths shorter then • Ultraviolet radiation has a wavelength between 200nm and

400nm.• UV type C (UVC), 100 - 280 nm. • UV type B (UVB), 280 - 315 nm.• UV type A (UVA), 315 - 400 nm. • Natural sunlight contains UV rays. Intense exposure to UV

rays can affect the human bodyMost of the solar UV radiations are UVA.*

• UVB de narrow band (311nm) and they have the lowest risk of causing cancer or solar burns.

Applications

• By wavelength:• 13.5 nm: Extreme Ultraviolet Lithography• 230-365 nm: UV-ID, label tracking, barcodes• 230-400 nm: Optical sensors, various instrumentation• 240-280 nm: Disinfection, decontamination of surfaces and water (DNA

absorption has a peak at 260 nm)• 200-400 nm: Forensic analysis, drug detection• 270-360 nm: Protein analysis, DNA sequencing, drug discovery• 280-400 nm: Medical imaging of cells• 300-320 nm: Light therapy in medicine• 300-365 nm: Curing of polymers and printer inks• 300-400 nm: Solid-state lighting• 350-370 nm: Bug zappers (flies are most attracted to light at 365 nm)