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Different Between UVA and UVB

uvaUVA vs UVB

UV refers to ultraviolet light. It is the electromagnetic radiation with a wavelength that is shorter than that of visible light but longer than x-rays. For that reason it is not visible to the human eye. It is named Ultraviolet means its spectrum has electromagnetic waves with frequencies higher than those that the human eye can identify as the color violet. There are various subtypes of UV light which include UVA and UVB, among others.

Among UV subtypes, UV subtype A or UVA has the longest wavelength measuring between 320 and 400 nanometers (nm) and has two other wave ranges within at 340 to 400nm and 320 to 400nm. Another subtype is the UV subtype B also known as UVB which has a range of 290 to 320nm. There’s a lot of exposure to UV light and especially UVA radiation because it has more prevalence than other subtypes owing to the fact that UVA radiation constitutes the largest percentage of UV radiation that penetrates through to the earth.


Ultraviolet light can have a negative effect on human skin if there’s over exposure. UVA being the most prevalent and with a longer wavelength can penetrate the skin deeply but although that is the case, its effects are less devastating compared to those caused by UVB light. UV light particularly UVA damages collagen fibers of the skin there by contributing to the speedy aging of the skin. Ultraviolet light especially UVA has a tanning effect which if exposed to for a period of time will cause the skin to tan. This is because of the damage to the DNA of the skin. As a result of the DNA damage, the skin will tan (darken) in an attempt to counter the damaging effects of the radiation but these imperfect alterations in DNA could lead to cancer. UVB on the other hand is only able to penetrate up to the epidermis layer, causing sunburn effects causing the skin to redden and it also speeds up the development of cancerous cells in the skin. Unlike UVA, UVB rays cannot penetrate glass and a big percentage of UVB light is reflected back from reflecting surfaces like glass.

1. UVA (320-400 nm) has a longer wavelength than UVB (290-320 nm).
2. UVA has more penetrating power and penetrates glass while UVB does not penetrate glass.
3. UVA radiation penetrates the skin up to the dermis layer while UVB only reaches the epidermis.
4. Although all UV radiation is harmful, UVB poses a higher risk factor than UVA because it causes direct DNA damage.

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  1. Very interesting article. Please supply booklets on UVA and UVB. Please send to P.O. Box 5235 Lacombe , AB T4L1W9. Canada.

  2. Are people aware of the damage caused to their DNA, epidermis and dermis by both UVA and UVB? Why do people like to tan? Are they not content with the colour of their skin given by the Creator?

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