Question

Ozone layer is present in:
A) mesosphere
B) lithosphere
C) stratosphere
D) none of these

Answer 1

Hint: The atmosphere is divided into many parts. Ozone layer is present in one of the layers of atmosphere. It’s the second major layer of Earth’s atmosphere.

Complete step-by-step answer:
Atmosphere is the layer which consists of all the kinds of gases present in the earth. This layer is held by the gravitational forces acting on the earth. The atmosphere is composed of nitrogen(78%), oxygen(21%) and other gases(1%).
Layers of atmosphere: Troposphere:The troposphere starts at the Earth's surface and extends 8 to 14.5 kilometers high (5 to 9 miles). This part of the atmosphere is the most dense. Almost all weather is in this region.
Stratosphere:The stratosphere starts just above the troposphere and extends to 50 kilometers (31 miles) high.
Mesosphere:The mesosphere starts just above the stratosphere and extends to 85 kilometers (53 miles) high. Meteors burn up in this layer
Thermosphere:The thermosphere starts just above the mesosphere and extends to 600 kilometers (372 miles) high. Aurora and satellites occur in this layer.
Ionosphere:The ionosphere is an abundant layer of electrons and ionized atoms and molecules that stretches from about 48 kilometers (30 miles) above the surface to the edge of space at about 965 km (600 mi), overlapping into the mesosphere and thermosphere. This dynamic region grows and shrinks based on solar conditions and divides further into the sub-regions: D, E and F; based on what wavelength of solar radiation is absorbed. The ionosphere is a critical link in the chain of Sun-Earth interactions. This region is what makes radio communications possible.
Exosphere:This is the upper limit of our atmosphere. It extends from the top of the thermosphere up to 10,000 km (6,200 mi).

$$\begin{array}{l}
\mathrm{O}_{2}+h v_{\mathrm{uv}} \rightarrow 2 \mathrm{O} \\
\mathrm{O}+\mathrm{O}_{2} \leftrightarrow \mathrm{O}_{3}
\end{array}
$$

In this other gases, ozone comprises 0.00006 %. This might seem a little percentage. But it is not. Ozone is one of the most important gases in the atmosphere.The ozone gas is present in the stratosphere level.
About 90 percent of the ozone in the atmosphere is contained in the stratosphere. Ozone concentrations are greatest between about 20 and 40 kilometres (66,000 and 131,000 ft), where they range from about 2 to 8 parts per million. If all of the ozone were compressed to the pressure of the air at sea level, it would be only 3 millimetres thick.

The answer is C)

Additional information: Ozone gas is one of the most important gases in the atmosphere.
The ozone layer or ozone shield is a region of the stratosphere that absorbs most of the Sun's ultraviolet
radiation. It contains a high concentration of ozone $\left(\mathrm{O}_{3}\right)$ in relation to other parts of the atmosphere,although still small in relation to other gases in the stratosphere. The ozone layer contains less than 10parts per million of ozone, while the average ozone concentration in Earth's atmosphere as a whole isabout 0.3 parts per million.This UV rays are very harmful to humans as they can cause skin cancer,etc.The Ozone layer helps us to overcome this illness.


Note: This ozone layer is even depleted over Antarctica. The concentration of ozone over this region has reduced to a significant level. This is called the ozone hole.