Free Environment and Atmosphere MCQs with Answers

51. __________ is the atmospheric layer wherein the weather occurs.

• A. Troposphere
• B. Stratosphere
• C. Mesosphere
• D. Thermosphere

Explanation: Most weather occurs in the troposphere because it contains most atmospheric water vapour and is heated from Earth's surface, producing convection, clouds and storms. The higher layers are much drier and more stable.

52. Atmospheric pressure is the force (per unit-area) perpendicular to a unit-area of planetary surface, as determined by _________.

• A. Mass of vertical column of atmospheric gases
• B. Mass of horizontal column of atmospheric gases
• C. Weight of vertical column of atmospheric gases
• D. Mass of vertical and weight of horizontal of atmospheric gases

Explanation: Atmospheric pressure is caused by the weight of the vertical column of air above a surface area. Mass alone is not a force, whereas weight is the gravitational force acting on that mass.

53. ___________ begins at 690 to 1,000 km from the surface, and extends to roughly 10,000 km.

• A. Troposphere
• B. Mesosphere
• C. Exosphere
• D. Stratosphere

Explanation: The exosphere is the outermost atmospheric layer, beginning roughly 690 to 1,000 km above Earth and extending thousands of kilometres into space. The troposphere, stratosphere, and mesosphere are much lower layers.

54. Which of the following is true about Ionosphere?

• A. Its density is lesser at short distances from planetary surface in morning and further decreases as ionosphere rises at night-time, thereby allowing a greater range of radio frequencies to travel greater distances
• B. Its density is greater at short distances from tplanetary surface in daytime and decreases as ionosphere rises at night-time, thereby allowing a greater range of radio frequencies to travel greater distances
• C. Its density is greater at long distances from planetary surface in daytime and further increases as ionosphere rises at night-time, thereby allowing a greater range of radio frequencies to travel greater distances
• D. None of the above

Explanation: The ionosphere is denser in its lower regions during daytime because solar radiation produces more ions, while reduced ionisation at night changes its height and radio-reflection behaviour. This simplified description matches option b; the actual ionosphere varies across several layers and frequencies.

55. Atmosphere is held in place by?

• A. Pressure of the planetary body
• B. Gravity of the planetary body
• C. Charge of the planetary body
• D. Heat of the planetary body

Explanation: Gravity pulls atmospheric gases toward a planet and prevents most of them from escaping into space. Pressure, charge, and heat can affect the atmosphere, but they do not hold it in place as gravity does.

56. The thermosphere extends from an altitude of ________ to the base of ________ at ________?

• A. 75 km, Mesosphere, 670 km
• B. 80 km, Ionosphere, 680 km
• C. 85 km, Exosphere, 690 km
• D. 90 km, Ozone Layer , 690 km

Explanation: In the simplified atmospheric model used here, the thermosphere begins near 85 km and extends to about 690 km, where the exosphere begins. Atmospheric boundaries are gradual and can vary slightly by reference source.

57. _________ is the layer wherein most meteors are incinerated before reaching the surface.

• A. Troposphere
• B. Stratosphere
• C. Mesosphere
• D. Ionosphere

Explanation: Most meteors burn up in the mesosphere because air resistance heats them intensely as they enter this layer. The ionosphere is a region of ionised gas that overlaps upper atmospheric layers, not the main meteor-burning layer.

58. The mesosphere ranges from ________ to _________?

• A. 46 km to 85 km
• B. 48 km to 85 km
• C. 50 km to 85 km
• D. 52 km to 85 km

Explanation: The mesosphere is conventionally described as extending from about 50 km to 85 km above Earth's surface. It lies above the stratosphere and below the thermosphere.

59. Stratosphere is the atmospheric layer that absorbs most of __________ that Earth receives from the Sun.

• A. Infrared radiation
• B. Ultraviolet radiation
• C. Ozone layer
• D. Radio waves

Explanation: The stratosphere contains the ozone layer, which absorbs most incoming ultraviolet radiation, especially harmful UV-B and UV-C. Infrared radiation is not the main radiation absorbed by this layer.

60. _________ is the atmospheric layer that absorbs most of the ultraviolet radiation that Earth receives from the Sun.

• A. Troposphere
• B. Stratosphere
• C. Mesosphere
• D. Ionosphere

Explanation: The stratosphere absorbs most solar ultraviolet radiation because it contains the ozone layer. The other layers do not contain the main concentration of atmospheric ozone responsible for this absorption.