Atmosphere

Total Questions: 29

11. Which atmospheric layer contains ozone layer? [S.S.C. Online CHSL (T-I) 15.01.2017(Shift-II)]

(a) Genosphere
(b) Zonosphere
(c) Stratosphere
(d) lonosphere

Correct Answer: (c) Stratosphere

Solution:The ozone layer is located in the stratosphere, which is the second layer of Earth's atmosphere above the troposphere.

Stratosphere:

Altitude: Approximately 15 to 50 km above Earth's surface
Contains the ozone layer, mainly between 20 to 30 km altitude
Function: Absorbs 95–99% of the Sun’s harmful ultraviolet (UV) radiation

12. By which layer of the atmosphere the ultraviolet rays are absorbed and scattered? [C.P.O. S.I. 6.06.2016 (Shift-I)]

(a) Troposphere
(b) Mesosphere
(c) Stratosphere
(d) Thermosphere

Correct Answer: (c) Stratosphere

Solution:The stratosphere is the main layer of the atmosphere that absorbs most of the Sun’s ultraviolet (UV) rays, thanks to the ozone layer present within it.

Absorption & Scattering of UV Rays:

UV Radiation Type	Absorbed By	Notes
UV-C (most harmful)	Completely absorbed by the ozone in the stratosphere	Fully blocked
UV-B	Partially absorbed by the ozone layer	Some reaches Earth
UV-A	Mostly passes through the atmosphere	Least harmful

Scattering of UV Rays:

Troposphere (lowest layer) contributes to scattering of UV rays due to air molecules, dust, and water vapor.
This scattering is what gives the sky its blue color.

13. What is the approximate percentage contribution of argon in Earth's atmosphere? [S.S.C. Online M.T.S. (T-I) 14.10.2021 (Shift-III)]

(a) 1%
(b) 2%
(c) 4%
(d) 3%

Correct Answer: (a) 1%

Solution:The percent of argon gas in our atmosphere is 0.932%, which is approximately 1%.

Major Gases in Earth's Atmosphere (by volume):

Gas	Percentage (%)
Nitrogen (N₂)	78.08%
Oxygen (O₂)	20.95%
Argon (Ar)	0.93%
Carbon dioxide (CO₂)	0.04% (varies)
Others (Ne, He, etc.)	< 0.01%

Argon is a noble gas—it is inert and does not readily react with other elements, making it stable in the atmosphere.

14. The most abundant element in the earth's atmosphere is- [S.S.C. Online C.G.L.(T-I) 4.09.2016 (Shift-II)]

(a) Argon
(b) Nitrogen
(c) Oxygen
(d) Krypton

Correct Answer: (b) Nitrogen

Solution:The most abundant element in the atmosphere is nitrogen. The Atmosphere contains 78% nitrogen.

15. By volume, 21% of air is ______ . [S.S.C. Online CHSL (T-I) 2.02.2018 (Shift-I)]

(a) Hydrogen
(b) Oxygen
(c) Nitrogen
(d) Carbon dioxide

Correct Answer: (b) Oxygen

Solution:By volume, 21% of air is Oxygen. Nitrogen is 78% and Carbon dioxide is approximately 0.03%

Major Gases in Earth's Atmosphere (by volume):

Gas	Percentage (%)
Nitrogen (N₂)	78.08%
Oxygen (O₂)	20.95%
Argon (Ar)	0.93%
Carbon dioxide (CO₂)	0.04% (varies)
Others (Ne, He, etc.)	< 0.01%

16. The percentage of nitrogen in air is about by volume. [S.S.C. Online MTS (T-I) 11.07.2022 (Shift-I)]

(a) 82%
(b) 78%
(c) 76%
(d) 74%

Correct Answer: (b) 78%

Solution:The percentage of nitrogen in air is about 78% by volume. This means that out of every 100 molecules in the air, about 78 are nitrogen molecules.

The remaining 21% of the air is mostly oxygen, with small amounts of other gases such as argon, carbon dioxide, neon, helium, and methane.

17. Which is the second most abundant gas in Earth's atmosphere? [S.S.C. Online CHSL (T-I) 16.10.2020 (Shift-I)]

(a) Carbon dioxide
(b) Nitrogen
(c) Hydrogen
(d) Oxygen

Correct Answer: (d) Oxygen

Solution:Oxygen is the second most abundant gas in Earth's atmosphere. The air in Earth's atmosphere is made up of approximately 21% oxygen.

Oxygen will be almost in negligible quantity at the height of 120 km. Oxygen is the most abundant element on Earth's crust.

Major Gases in Earth's Atmosphere (by volume):

Gas	Percentage (%)
Nitrogen (N₂)	78.08%
Oxygen (O₂)	20.95%
Argon (Ar)	0.93%
Carbon dioxide (CO₂)	0.04% (varies)
Others (Ne, He, etc.)	< 0.01%

18. Which two gases are having the highest percentage of the earth's atmosphere? [S.S.C. Online CHSL (T-1) 06.06.2022 (Shift-II)]

(a) Nitrogen and Oxygen
(b) Nitrogen and Hydrogen
(c) Oxygen and carbon monoxide
(d) Carbon dioxide and nitrogen

Correct Answer: (a) Nitrogen and Oxygen

Solution:

The two gases with the highest percentage in Earth's atmosphere are:

Nitrogen (N₂) – 78.08%
Oxygen (O₂) – 20.95%

These two gases together make up about 99% of the Earth's atmosphere.

19. Which of the following is a unit of measurement of the ozone layer? [C.P.O.S.I. 4.06.2016 (Shift-I)]

(a) Dobson unit
(b) Gordon unit
(c) Warhol unit
(d) Tatum unit

Correct Answer: (a) Dobson unit

Solution:Dobson is the unit of measurement of the ozone layer.

Dobson Unit (DU): Key Facts

It measures the total amount of ozone in a column of the atmosphere from the surface to the top.
1 Dobson Unit = 0.01 mm thickness of pure ozone at standard temperature and pressure (STP).
Normal values of ozone range from 200 to 500 DU, depending on location and season.

20. Ozone depletion is greatest near: [S.S.C. Online Constable GD 18.02.2019 (Shift-II)]

(a) oceans
(b) equator
(c) poles
(d) tropics

Correct Answer: (c) poles

Solution:Ozone depletion is greatest near the poles, especially the South Pole (Antarctica).

Why Depletion Is Greatest Near the Poles:

Reason	Explanation
Cold temperatures	Promote the formation of polar stratospheric clouds that aid in ozone-destroying chemical reactions.
Presence of CFCs and halons	These man-made chemicals release chlorine and bromine, which destroy ozone molecules.
Seasonal sunlight	In spring (September–October in Antarctica), returning sunlight triggers reactions that rapidly deplete ozone.

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Atmosphere

11. Which atmospheric layer contains ozone layer? [S.S.C. Online CHSL (T-I) 15.01.2017(Shift-II)]

Stratosphere:

12. By which layer of the atmosphere the ultraviolet rays are absorbed and scattered? [C.P.O. S.I. 6.06.2016 (Shift-I)]

Absorption & Scattering of UV Rays:

Scattering of UV Rays:

13. What is the approximate percentage contribution of argon in Earth's atmosphere? [S.S.C. Online M.T.S. (T-I) 14.10.2021 (Shift-III)]

14. The most abundant element in the earth's atmosphere is- [S.S.C. Online C.G.L.(T-I) 4.09.2016 (Shift-II)]

15. By volume, 21% of air is ______ . [S.S.C. Online CHSL (T-I) 2.02.2018 (Shift-I)]

Major Gases in Earth's Atmosphere (by volume):

16. The percentage of nitrogen in air is about by volume. [S.S.C. Online MTS (T-I) 11.07.2022 (Shift-I)]

17. Which is the second most abundant gas in Earth's atmosphere? [S.S.C. Online CHSL (T-I) 16.10.2020 (Shift-I)]

Major Gases in Earth's Atmosphere (by volume):

18. Which two gases are having the highest percentage of the earth's atmosphere? [S.S.C. Online CHSL (T-1) 06.06.2022 (Shift-II)]

19. Which of the following is a unit of measurement of the ozone layer? [C.P.O.S.I. 4.06.2016 (Shift-I)]

Dobson Unit (DU): Key Facts

20. Ozone depletion is greatest near: [S.S.C. Online Constable GD 18.02.2019 (Shift-II)]

Why Depletion Is Greatest Near the Poles:

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