Question

What is your familiarity with the terms infrared and ultraviolet? What uses and/or risks do they pose to humans?

Answer 1

Both ultraviolet and infrared energy are invisible to the human eye.

Infrared (IR) is heat energy, so it can damage the skin (burn). IR has a longer wavelength, however, so it won't penetrate the skin deeply

UV energy, because of its shorter wavelength, has the capability of penetrating more deeply into the skin, and in doing so damaging deeper layers of skin cells. In addition, UV light is dangerous because it can mutate DNA.

Answer 2

Re-word this:

Infrared: (of electromagnetic radiation) having a wavelength just greater than that of the red end of the visible light spectrum but less than that of microwaves. Infrared radiation has a wavelength from about 800 nm to 1 mm, and is emitted particularly by heated objects.

Ultraviolet: (of electromagnetic radiation) having a wavelength shorter than that of the violet end of the visible spectrum but longer than that of X-rays.

Answer 3

You are right...

Answer 4

Wait, I have one question: isn't intense UV light blue?
When I disinfect a BSL-1 safety hood in the lab, it glows light blue from the UV rays.

Answer 5

NM you are right.
Thoe light wavelengths are probably not pure UV

Answer 6

First, Thanks for your re - write my sentences.

Second, well...I don't know with that question... What do you think?

Answer 7

Sorry, you are correct.

Answer 8

Oh thanks for the medal...well actually. I did nothing. You are the one who help me with. Anyways...thanks :)

Answer 9

Oh Okay..... no problem :)

Answer 10

You might be able to draw some ideas from here:
(It's wikipedia, so don't rely just on it, use it for ideas):

The differential effects of various wavelengths of light on the human cornea and skin are sometimes called the "action spectrum.".[30] The action spectrum shows that UVA does not cause immediate reaction, but rather UV begins to cause photokeratitis and skin redness (with Caucasians more sensitive) at wavelengths starting near the beginning of the UVB band at 315 nm, and rapidly increasing to 300 nm. The skin and eyes are most sensitive to damage by UV at 265-275 nm, which is in the lower UVC band. At still shorter wavelengths of UV damage continues to happen, but the overt effects of inflammation are not as great. The WHO-standard ultraviolet index is a widely publicized measurement of total strength of UV wavelengths that cause sunburn on human skin, by correcting UV exposure for action spectrum effects for UV light on a given day and time. This standard shows that most sunburn happens due to UV at wavelengths near the boundary of the UVA and UVB bands.

Overexposure to UVB radiation not only can cause sunburn but also some forms of skin cancer. However, the degree of redness and eye irritation (which are largely not caused by UVA) do not predict the long term effects of UV, although they do mirror the direct damage of DNA by ultraviolet. The World Health Organization (WHO) classifies all categories and wavelengths of ultraviolet radiation as a Group 1 carcinogen.

In humans, excessive exposure to all bands of UV radiation can result in chronic harmful effects on the skin, eye, and immune system.[31] All bands of UV radiation damage collagen fibers and accelerate aging of the skin. Both UVA and UVB destroy vitamin A in skin, which may cause further damage.[32]

UVB light can cause direct DNA damage.[33] The mutagenicity of UV radiation can be observed in bacterial cultures. This cancer connection is one reason for concern about ozone depletion and the ozone hole.


Demonstration of the effect of sunscreen. The man's face has sunscreen on his right only. The left image is a regular photograph of the face; the right image is taken by reflected UV light. The side of the face with sunscreen is darker because the sunscreen absorbs the UV light.
Medical organizations recommend that patients protect themselves from UV radiation by using sunscreen. Five sunscreen ingredients have been shown to protect mice against skin tumors. However, some sunscreen chemicals produce potentially harmful substances if they are illuminated while in contact with living cells.[34][35]

Ultraviolet radiation can aggravate several skin conditions and diseases, including rosacea, lupus and others.[36]

Eye damage[edit]
The eye is most sensitive to damage by UV in the lower UVC band at 265-275 nm. Light of this wavelength is almost absent from sunlight, but is found in welder's arc lights and other artificial sources. Exposure to these causes welder's flash or arc eye (photokeratitis), and can lead to cataracts, pterygium,[37][38] and pinguecula formation. To a lesser extent, UVB in sunlight from 310-280 nm also causes photokeratitis ("snow blindness"), and the cornea, the lens, and the retina can be damaged.

Protective eyewear is beneficial to those exposed to ultraviolet radiation. Since light can reach the eyes from the sides, full-coverage eye protection is usually warranted if there is an increased risk of exposure, as in high-altitude mountaineering. Mountaineers are exposed to higher-than-ordinary levels of UV radiation, both because there is less atmospheric filtering and because of reflection from snow and ice.

Ordinary, untreated eyeglasses give some protection. Most plastic lenses give more protection than glass lenses, because, as noted above, glass is transparent to UVA and the common acrylic plastic used for lenses is less so. Some plastic lens materials, such as polycarbonate, inherently block most UV. Protective coating is available for eyeglass lenses that need it, but even a coating that completely blocks UV will not protect the eye from light that arrives around the lens.

Degradation of polymers, pigments and dyes[edit]
Main article: UV degradation

UV damaged polypropylene rope (left) and new rope (right)
UV degradation is one form of polymer degradation that affects plastics exposed to sunlight. The problem appears as discoloration or fading, cracking, loss of strength or disintegration. The effects of attack increases with exposure time and sunlight intensity. The addition of UV absorbers inhibits the effect.

Sensitive polymers include thermoplastics and speciality fibers like aramids. UV absorption leads to chain degradation and loss of strength at sensitive points in the chain structure. Aramid rope must be shielded with a sheath of thermoplastic if it is to retain its strength.


IR spectrum showing carbonyl absorption due to UV degradation of polyethylene
Many pigments and dyes absorb UV and change colour, so paintings and textiles may need extra protection both from sunlight and fluorescent bulbs, two common sources of UV radiation. Window glass absorbs some harmful UV, but valuable artifacts need extra shielding. Many museums place black curtains over watercolour paintings and ancient textiles, for example. Since watercolours can have very low pigment levels, they need extra protection from UV light.