The ozone layer restricts

The ozone layer restricts

A. Visible light
B. Infrared radiation
C. X-rays and gamma rays
D. Ultraviolet radiation



Answer: The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet (UV) radiation.


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Ozone layer

The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet (UV) radiation. It contains high concentrations of ozone (O3) in relation to other parts of the atmosphere, although still small in relation to other gases in the stratosphere. 

The ozone layer restricts

The ozone layer contains less than 10 parts per million of ozone, while the average ozone concentration in Earth's atmosphere as a whole is about 0.3 parts per million. 

The ozone layer is mainly found in the lower portion of the stratosphere, from approximately 20 to 30 kilometres (12 to 19 mi) above Earth, although its thickness varies seasonally and geographically.

Exposure to sunlight helps a person improve his health because

Exposure to sunlight helps a person improve his health because

A. the infrared light kills bacteria in the body
B. resistance power increases
C. the pigment cells in the skin get stimulated and produce a healthy tan
D. the ultraviolet rays convert skin oil into Vitamin D



Answer: D

Source:

Health effects of sunlight exposure

The ultraviolet radiation in sunlight has both positive and negative health effects, as it is both a principal source of vitamin D3 and a mutagen.

Exposure to sunlight helps a person improve his health because

Vitamin D has a wide range of positive health effects, which include strengthening bones[2] and possibly inhibiting the growth of some cancers.

UV exposure also has positive effects for endorphin levels, and possibly for protection against multiple sclerosis. Visible sunlight to the eyes gives health benefits through its association with the timing of melatonin synthesis, maintenance of normal and robust circadian rhythms, and reduced risk of seasonal affective disorder.

A 2016 review of studies shows a range of benefits from healthy sun or UV exposure affecting cancer, cardiovascular disease, Alzheimer disease and dementia, myopia and macular degeneration, diabetes and multiple sclerosis.

Long-term sunlight exposure is known to be associated with the development of skin cancer, skin aging, immune suppression, and eye diseases such as cataracts and macular degeneration.

Short-term over-exposure is the cause of sunburn, snow blindness, and solar retinopathy.

UV rays, and therefore sunlight and sunlamps, are the only listed carcinogens that are known to have health benefits,and a number of public health organizations state that there needs to be a balance between the risks of having too much sunlight or too little.

There is a general consensus that sunburn should always be avoided.

Link:
Sun Exposure, Skin Cancer, and Other Sun Damage