Class 9 Social Science Part 1 Chapter 3 MCQ – Atmosphere and Climate

Gravity attracts atmospheric gases towards the Earth. This surrounding blanket of air supports life, influences weather and helps regulate the planet’s temperature.

Nitrogen makes up about 78 percent of the atmospheric mixture shown. Oxygen is next at about 21 percent, while other gases occur in much smaller proportions.

Water vapour enters the air through evaporation. When conditions allow it to condense and droplets or ice particles grow, clouds and precipitation can develop.

Air is densest close to the Earth’s surface and becomes thinner with height. This vertical variation is part of the atmosphere’s layered structure described in the chapter.

The troposphere contains most atmospheric water vapour and clouds. Rain, fog and hail therefore mainly occur here, making it the layer most directly connected with everyday weather.

The tropopause is the transition zone above the troposphere. Beyond it lies the stratosphere, which has different temperature behaviour and generally more stable conditions.

The ozone layer lies in the stratosphere and filters harmful ultraviolet radiation from the Sun. This protective function helps shield living organisms at the surface.

The chapter connects stratospheric stability with flying conditions. Compared with the lower atmosphere, fewer clouds and ordinary weather disturbances can provide smoother conditions for aircraft.

The mesosphere lies above the stratosphere. Most meteors burn up in this region, which helps prevent many small incoming space objects from reaching the ground.

Charged particles from the Sun are guided towards magnetic polar regions. Their interactions with atmospheric gases produce light, creating the northern and southern auroras.

The exosphere is the uppermost atmospheric layer described in the chapter. Its gases are very thinly spread, and light particles can escape towards space.

Climate describes weather patterns and variations over a long period, commonly thirty years or more. Weather refers to short-term atmospheric conditions at a particular time.

Insolation is incoming energy from the Sun. Differences in how this energy reaches the Earth help explain variations in temperature between places and seasons.

More direct rays concentrate solar energy over a smaller surface area. At higher latitudes, lower-angle sunlight spreads its energy more widely, contributing to cooler conditions.

Humidity refers to water vapour in the air. When surrounding air is already moist, evaporation is slower, so clothes take longer to dry and sweat evaporates less readily.

Precipitation is water falling from the atmosphere to the surface. It includes liquid forms such as rain and solid or mixed forms such as snow, sleet and hail.

Atmospheric pressure is exerted by the weight of air. At greater heights, there is less overlying air, so pressure generally becomes lower than at sea level.

Pressure differences drive air from higher-pressure towards lower-pressure areas. The Earth’s rotation and other factors influence its actual direction, but pressure differences are fundamental to wind.

Winds are named for the direction from which they originate. A westerly comes from the west, even though it moves generally towards the east.

During the day, land becomes warmer than nearby water. Rising warm air creates relatively lower pressure over land, drawing cooler air inland from the sea.

At night, land cools more quickly than surrounding water. The resulting pressure difference encourages air to move from the cooler land towards the relatively warmer sea.

Monsoon refers to seasonal reversal of wind direction. Changing land-sea heating and pressure patterns produce distinct circulation patterns that strongly influence rainfall and life in India.

Summer heating creates relatively low pressure over the subcontinent. Moist air moves towards the land from surrounding seas, bringing much of India’s annual rainfall.

Although many winter winds begin over land, those crossing the Bay of Bengal collect moisture. They can then bring important rainfall to parts of southeastern India.

Monsoon rainfall supports sowing, crop growth and water storage. Its amount and distribution affect farm production, related employment and households that depend on agriculture.

The National Monsoon Mission develops weather and climate prediction capabilities. Better monsoon forecasts can support planning in agriculture, water management and other activities affected by seasonal rainfall.

Walking and cycling avoid fuel use during the journey. For suitable short trips, these choices reduce transport-related emissions compared with using a private motor vehicle.

Burning fossil fuels releases carbon dioxide and strengthens human influence on the climate. Reducing unnecessary energy use and shifting to cleaner energy can help limit emissions.

The case study combines natural causes with human factors. Heavy rainfall swelled rivers, while weak embankments, encroachment, silt accumulation and inadequate warnings increased exposure and damage.

Clear warnings give people time to act, while evacuation planning identifies safer routes and places. Preparedness can reduce losses even when heavy rainfall cannot be prevented.