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Directions (Q. No. 11 to 15):

Read the following text and answer the following questions on the basis of the same:

Ozone layer depletion:

We are all exposed to UV radiation from the sun.

The sun is by far the strongest source of ultraviolet radiation. UV radiation spectrum is divided into three regions called UVA, UVB and UVC. As sunlight passes through the atmosphere, all UVC and most UVB is absorbed by ozone, water vapour, oxygen and carbon dioxide. UVA is not filtered as significantly by the atmosphere.

The three types of UV radiation are classified according to their wavelength. They differ in their biological activity and the extent to which they can penetrate the skin. The shorter the wavelength, the more harmful the UV radiation.

The UV region covers the wavelength range 100-400 nm and is divided into three bands:

• UVA (315-400 nm)

• UVB (280-315 nm)

• UVC (100-280 nm).

Short-wavelength UVC is the most damaging type of UV radiation. However, it is completely filtered by the atmosphere and does not reach the earth's surface.

UV level reaching the earth changes with latitude and altitude.

UV levels are higher closer to the equator, Closer to the equator the sun's rays have a shorter distance to travel through the atmosphere and therefore harmful UV radiation absorption is less.

With increasing altitude less atmosphere is available to absorb UV radiation. With every 1000 m in altitude, UV levels increase by approximately 10% Ozone is a particularly effective absorber of UV radiation. As the ozone layer gets thinner, the protective filter activity is progressively reduced.

Consequently, the people and the environment are exposed to higher levels of UV radiation, especially UVB.

Ozone depletion is caused by human-made chemicals released into the atmosphere.

How many bands are there in UV radiation spectrum?

A) 2

B) 5

C) 3

D) 4