Atmosphere or Earth’s atmosphere is the layer of gases surrounding our planet. It is commonly known as air and is essential for sustaining life on the earth. Earth’s atmosphere provides us with oxygen to breathe. It absorbs and protects us from the harmful ultraviolet radiation of sunlight. It warms the earth’s surface by trapping heat through the greenhouse effect and minimises the diurnal temperature variation. The four main layers of the atmosphere are troposphere, stratosphere, mesosphere and thermosphere starting from the nearest to the farthest from the earth. The atmosphere consists of mainly three gases, viz., nitrogen (78.09%), oxygen (20.94%) and argon (0.93%). Other gases include carbon dioxide (0.04%), methane and other inert gases. Air also consists of water vapour, which varies at different locations.

1. The term biosphere refers to

(a) Rocks and minerals

(b) Plants and animals

(c) Water sources

(d) Atmosphere and lithosphere

Answer: (b)

2. The boundary between troposphere and stratosphere is known as

(a) tropopause

(b) ionopause

(c) stratopause

(d) mesopause

Answer: (a)

3. Ozone hole is

(a) increase in the concentration of ozone

(b) hole in the ozone layer

(c) depletion of the ozone layer in the troposphere

(d) depletion of the ozone layer in the stratosphere

Answer: (d)

4. If an object is present at a distance of 5 km from the surface of the earth, it is present in

(a) Troposphere

(b) Thermosphere

(c) Mesosphere

(d) Stratosphere

Answer: (a)

5. The uppermost layer of atmosphere is known as

(a) Ionosphere

(b) Troposphere

(c) Stratosphere

(d) Exosphere

Answer: (d)

6. Which among the following does not cause pollution?

(a) Automobiles

(b) Thermal power plant

(c) Hydro-electric plant

(d) Nuclear power plant

Answer: (c)

7. The equipment to measure atmospheric humidity is

(a) Anemometer

(b) Psychrometer

(c) Hydrometer

(d) Lysimeter

Answer: (b)

8. The mass of water vapour in a unit mass of air is referred to as

(a) relative humidity

(b) specific humidity

(c) approximate humidity

(d) absolute humidity

Answer: (b)

9. The ozone layer is present in

(a) Thermosphere

(b) Stratosphere

(c) Troposphere

(d) Mesosphere

Answer: (b)

10. The main constituents of atmosphere are

(a) N₂ and O₂

(b) CO₂ and N₂

(c) CO and CO₂

(d) O₃ and SO₂

Answer: (a)