Atmosphere and Temperature: NCERT Solutions (2026)
Welcome to ExamSpark! If you are a Class 9 student preparing for your CBSE 2026 exams, you know that Geography can sometimes feel overwhelming. Atmosphere and Temperature is a core chapter that forms the base for all your future Geography concepts—even if you plan to crack CUET in a few years!
In this chapter, we learn about the invisible blanket of air surrounding our Earth, what it's made of, and how it heats up. You'll understand real-life applications, like why hill stations are colder than plains and how the ozone layer protects us. Many students struggle with the concepts of Insolation and Normal Lapse Rate, losing easy marks. The funde (basics) here need to be crystal clear!
Don't worry, tension lene ki zaroorat nahi hai. These complete NCERT solutions, extra board questions, PYQs, and MCQs will make your preparation solid. Every solution is written in easy Indian student language so you can memorize it quickly and score full marks!
Quick Answer: What is Chapter 3 Atmosphere and Temperature about?
Chapter 3 explains the composition and structure of the Earth's atmosphere. It covers the five atmospheric layers, the distribution of temperature across the globe, the concept of insolation, the heat budget, and the factors affecting the temperature of different regions.
Learning Objectives
- Define the atmosphere and understand its vital importance to life on Earth.
- List the major gases that make up the atmospheric composition.
- Differentiate between the five structural layers of the atmosphere.
- Explain the concept of Insolation and the Earth's Heat Budget.
- Understand why temperature decreases with altitude and identify the heat zones on a map.
Key Concepts and Definitions
Main Idea: The Earth's climate is controlled by the atmosphere's composition and how it absorbs solar energy. Nitrogen (78%) and Oxygen (21%) dominate the air.
- Atmosphere: The thick envelope of air surrounding the Earth, held by gravity.
- Troposphere: 0-13 km. Weather layer. Temperature decreases with height.
- Stratosphere: 13-50 km. Contains Ozone ($O_3$) which absorbs harmful UV rays. Ideal for flying airplanes.
- Mesosphere: 50-80 km. Meteorites burn up here.
- Insolation: INcoming SOLar radiATION. The sun's energy intercepted by Earth.
- Normal Lapse Rate: The rate at which temperature drops with height ($1^\circ C$ per 165m).
- Albedo: The proportion of solar light reflected by the Earth's surface without heating the Earth.
- Heat Budget: The perfect balance between incoming heat from the sun and outgoing heat from Earth.
COMPLETE NCERT SOLUTIONS
Question 1: What is the atmosphere? What is its significance?
The atmosphere is a vast expanse of air (a mixture of gases) that completely surrounds the Earth and is held in place by Earth's gravitational pull.
Significance:
- It provides Oxygen for breathing and Carbon Dioxide for photosynthesis.
- The ozone layer protects life from the Sun's harmful Ultraviolet (UV) rays.
- It regulates Earth's temperature, preventing it from becoming too hot during the day or too cold at night (Greenhouse effect).
Question 2: Write down the composition of the atmosphere.
The atmosphere is primarily composed of the following gases:
- Nitrogen: 78.08% (Helps in plant growth)
- Oxygen: 20.95% (Essential for respiration and combustion)
- Argon: 0.93% (Inert gas)
- Carbon Dioxide: 0.03% (Absorbs heat, essential for plants)
- Traces of other gases like Neon, Helium, Hydrogen, and water vapor.
Question 3: Explain the structure of the atmosphere with the help of a diagram.
The atmosphere is divided into five distinct layers based on temperature and density:
- Troposphere: The lowest layer (up to 13 km). All weather phenomena (rain, clouds, storms) happen here.
- Stratosphere: Extends up to 50 km. It is free from clouds, making it perfect for flying aeroplanes. It contains the protective Ozone layer.
- Mesosphere: Extends up to 80 km. Meteorites entering Earth's atmosphere burn up in this layer due to friction.
- Thermosphere (Ionosphere): Extends up to 400 km. Radio waves transmitted from Earth are reflected back by this layer, enabling wireless communication.
- Exosphere: The outermost layer. It has very thin air, mainly consisting of light gases like Helium and Hydrogen, merging into outer space.
(Exam Tip: Always draw a neat, labeled block diagram showing these 5 layers with their altitude in exams!)
Question 4: What is Insolation?
Insolation stands for Incoming Solar Radiation. It is the solar energy received and intercepted by the Earth. The amount of insolation decreases as we move from the equator towards the poles because the sun's rays become slanting.
Question 5: Why does temperature decrease with increasing altitude?
The atmosphere is heated from below by the Earth's surface (terrestrial radiation), not directly from the Sun. Therefore, the air closest to the Earth is warmer. As we go higher into the troposphere, the air becomes less dense and holds less heat. The temperature decreases at a rate of $1^\circ C$ for every 165 meters of ascent, known as the Normal Lapse Rate.
Question 6: List the factors that control the distribution of temperature on Earth.
The distribution of temperature is controlled by:
- Latitude: Places near the equator get direct sunlight and are hotter.
- Altitude: Higher places (like Shimla) are cooler than plains (like Delhi).
- Distance from the Sea: Coastal areas experience moderate climates due to land and sea breezes, while inland areas face extreme temperatures.
- Ocean Currents: Warm currents raise the temperature of coastal areas, while cold currents lower it.
- Relief Features: Mountains act as barriers to cold or hot winds.
Question 7: What are the heat zones of the Earth?
The Earth is divided into three heat zones based on the amount of insolation received:
- Torrid Zone: Between Tropic of Cancer and Tropic of Capricorn. Receives direct sunlight, maximum heat.
- Temperate Zone: Between Tropics and Arctic/Antarctic circles. Slanting rays, moderate temperature.
- Frigid Zone: Between polar circles and the poles. Extremely slanting rays, very cold throughout the year.
EXTRA IMPORTANT QUESTIONS (BOARD STYLE 2026)
Short Answer Questions (2-3 Marks)
Q1. Define Albedo.
Answer: The amount of incoming solar radiation reflected back into space by the Earth's surface (clouds, ice, etc.) without heating the Earth is called Albedo.
Q2. What is Terrestrial Radiation?
Answer: The long-wave heat energy radiated back into the atmosphere by the heated surface of the Earth during the night.
Q3. Why do mountain climbers carry oxygen cylinders? (HOTS)
Answer: As altitude increases, atmospheric pressure decreases, and the air becomes thinner. The amount of available oxygen drops significantly, causing breathing difficulties.
Q4. Differentiate between weather and climate.
Answer: Weather is the day-to-day atmospheric condition of a specific place, while climate is the average weather pattern of a large area over a long period (usually 30+ years).
Long Answer Questions (5 Marks)
Q5. Explain Earth's Heat Budget.
Answer: The Heat Budget is the balance between incoming insolation and outgoing terrestrial radiation. If Earth receives 100 units of heat, roughly 35 units are reflected into space (albedo). The remaining 65 units are absorbed by the atmosphere and Earth's surface. Eventually, these 65 units are radiated back into space, ensuring the Earth neither heats up nor cools down drastically over time.
Q6. Why is the Ozone layer important and how is it being depleted?
Answer: Ozone ($O_3$) absorbs harmful UV rays that cause skin cancer. It is being depleted by Chlorofluorocarbons (CFCs) used in refrigerators and ACs.
Case-Based & Competency Questions
Case 1: Rahul visited Shimla during summer vacations while his friend stayed in Delhi. Rahul needed a jacket, but his friend was using an AC.
Q1: Which factor of temperature distribution is highlighted here?
Answer: Altitude.
Q2: Explain the phenomenon causing this.
Answer: Normal Lapse Rate; temp decreases $1^\circ C$ per 165m height.
Case 2: A pilot prefers to fly commercial aircraft above the clouds to give passengers a smooth ride.
Q1: Which atmospheric layer is the pilot flying in?
Answer: Stratosphere.
Q2: Why is this layer preferred?
Answer: It lacks weather phenomena and strong vertical winds.
Calculation Competency: If the Normal Lapse Rate is $1^\circ C$ per 165m, and sea level temp is $30^\circ C$, what is the temp at 1650m?
Answer: Height = 1650m. Temp drop = $1650 / 165 = 10^\circ C$. Final temp = $30 - 10 = 20^\circ C$.
Assertion-Reason Questions
(A) Both true & R explains A | (B) Both true but R doesn't explain A | (C) A is true R is false | (D) A is false R is true.
1. Assertion (A): Troposphere is the most important layer for humans.
Reason (R): All weather happens here.
Answer: (A) Both are true and R is the correct explanation.
2. Assertion (A): Temperature decreases as we go up.
Reason (R): The sun is further away.
Answer: (C) A is true but R is false. Earth is heated from below (terrestrial radiation), not directly by proximity to the sun in the lower atmosphere.
COMMON MISTAKES STUDENTS MAKE
- Confusing Insolation with Terrestrial Radiation: Insolation comes from the Sun (short wave). Terrestrial radiation goes from Earth to space (long wave).
- Diagram Labeling: Drawing the atmospheric layers without labeling the altitudes. Always mark 13km, 50km, 80km, etc.
- Heating Logic: Thinking we are heated directly by the sun's rays. Reality: The sun heats the ground, and the ground heats the air above it!
- Spelling: Troposphere and Stratosphere often get mixed up. Remember: Troposphere touches the Terrain.
Frequently Asked Questions (FAQ)
Q1. Is Chapter 3 Atmosphere and Temperature important for Class 9 boards?
Yes, it carries 4-5 marks and builds the foundation for the "Climate" chapter.
Q2. How many layers are in the atmosphere?
There are five main layers: Troposphere, Stratosphere, Mesosphere, Thermosphere, and Exosphere.
Q3. What is the normal lapse rate?
It is the decrease in temperature by $1^\circ C$ for every 165 meters of altitude gained.
Q4. What is the difference between Insolation and Radiation?
Insolation is incoming solar energy, while radiation is the heat released back by the Earth.
Q5. Why is the stratosphere ideal for flying?
Because it is above the weather layer (troposphere), meaning no storms, clouds, or heavy turbulence.
CONCLUSION
Understanding the Atmosphere and Temperature isn't just for passing exams—it's about knowing how our world works! The concept of the Normal Lapse Rate is the exact reason why you escape to hill stations like Manali during summer vacations.
Make sure you draw the 5 atmospheric layers on a blank sheet a few times. Focus on the Heat Budget for your long answers, and you will easily secure top marks in your 2026 Board Exams. You've got this!