How ultraviolet & infrared rays affect the human body?
A. The human eyes can’t see ultraviolet and infrared rays,
however, they have diverse impacts on the human body. The visible light ranges
from 400 to 700 nm whereas ultraviolet rays range lies between 1 to 400 nm and
infrared rays range lies beyond 700 nm. As shown in the below picture, the
ultraviolet rays are classified in three different categories depending on the
wavelength. UV-A (320-380nm), UV-B (290-320 nm) and UV-C (<200). UV-A is
responsible for tanning effect on human body. UV-B activates Vitamin D and the
absorption of calcium and other minerals in the body. UV-C is harmful and
absorbed by the Ozone layer surrounding the earth. The overexposure to
ultraviolet rays may cause skin cancer though. UV rays with wavelength shorter
than 300 nm are effective in killing bacteria and viruses. Therefore, the UV
lamps are used to sterilize surgical instruments in hospitals, water and the
air in operation theaters. The water purifier is also equipped with UV lamps to
destroy infectious bacteria and germs. Many food and drug companies use UV
lamps for disinfestations of various types of products and their containers.