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Ultraviolet Light (The electromagnetic (EM) spectrum (visible light,…
Ultraviolet Light
The electromagnetic (EM) spectrum
visible light
ultraviolet (UV)
infrared (IR)
X-rays
microwaves
gamma-rays
radio waves
Range
between visible light and X-rays
3 sub-bands
UVA, or near UV (315-400 nm)
UVB, or middle UV (280-315 nm)
UVC, or far UV (180-280 nm)
vacuum or extreme UV (10 nm to 180 nm)
UV effects
10% of sunlight is UV, one-third of this reach the ground
95% is UVA, 5% is UVB, 0% is UVC
UVA and UVB are the strongest and most damaging to living things
Sunburn
Melanin is a natural sunscreen
However, continued exposure to UV radiation
can overwhelm the body's defenses
People who get sunburned repeatedly are
at much higher risk (skin cancer)
Ionization
UV can break chemical bonds
useful for chemical processing
damaging to materials and living tissues (skin, eyes)
Introduce
summer tans, sunburns
damaging to living tissue
Other UV sources
Tanning booths, black lights, curing lamps,
germicidal lamps, mercury vapor lamps, halogen lights,
high-intensity discharge lamps, fluorescent and
incandescent sources, and some types of lasers
Light-emitting diodes (LEDs), lasers and arc lamps
UV astronomy
using high-altitude balloons and orbiting telescopes equipped for observing in the UV region of the EM spectrum
most observations are conducted using charge-coupled devices (CCD), detectors designed to be
sensitive to short-wavelength photons
Cancer treatment
While exposure to UV light can lead to skin cancer, some skin conditions can be treated using UV light
(psoralen ultraviolet light treatment - PUVA)
PUVA slows down the growth that plays a major role
in the disease’s development
Fluorescence
Many substances can absorb UV radiation
and appear brighter under sunlight
used for signs, safety vests and other
applications in which high visibility is important
Key to the origin of life?
Recent research suggests that UV light may have played a key role in the origin of life on Earth