Question

In the upper atmosphere_______ becomes the ozone, a substance that protects the earth from UV radiations and makes life on land possible.
A. Carbon Dioxide
B. Oxygen
C. Nitrogen
D. Water vapour

Answer 1

Hint: Oxygen is a crucial gas for aerobic respiratory organisms, which utilize oxygen for production of energy and digestion of food. 21 percent of oxygen present in our earth atmosphere along with other major Nitrogen 78 percent, carbon dioxide 0.03 present and some other rare inert gases.

Complete answer:
Oxygen found in lower earth atmosphere below the troposphere as in O2 form and with water as compound form, plants utilize the carbon dioxide and water to produce energy and release oxygen into the atmosphere, this oxygen comes out by hydrolysis of water molecules in plants in the presence of sunlight.

In the upper atmosphere, that means above the troposphere this oxygen is found in O3 form, which is chemically called as ozone which is present in the stratospheric region of atmosphere, in this region temperature is around -5O celsius. In this region oxygen atoms combine and form ozone molecules because they trap the harmful short wave radiation called ultra violet radiation. Basically UV-C and B are trapped and required to form an ozone layer and UV-C is passed out from this trap because it is much larger wavelength than UV-A and UV-B.

90 percent of ozone is present in the stratosphere and 10 percent is present in the tropospheric region. Ozone is measured in a Dobson unit and 1 Dobson unit (DU) is equal to 0.1 in length.

Hence, the correct answer is option (B).

Note: Ozone is necessary layer to protect the earth living being from harmful radiation that may affect the life on earth and prolonged exposure to such UV radiation can cause skin cancer and irritation in eyes, now past few decades ozone layer is depleted over antarctica region due to emission of CFCs, which further cause rising in sea level.