Science Exploration Notes Class 9 English Medium 2026-27

Science Exploration Chapter 13. Earth as a System: Energy, Matter, and Life

CBSE Notes New Syllabus: Class 9

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Chapter 13. Earth as a System: Energy, Matter, and Life

This section explains how solar radiation interacts with the Earth's atmosphere and surface. It describes reflection, absorption, scattering and the concept of albedo. It also explains why different regions of the Earth receive unequal amounts of solar energy, leading to variations in weather and climate. 

Interaction of Solar Radiation with the Earth

What Happens to Solar Radiation?

When solar radiation reaches the Earth, it does not entirely reach the surface. Part of it is reflected back into space, some is absorbed by the atmosphere and the Earth's surface, while the remaining energy is scattered in different directions. These processes regulate the Earth's temperature and climate. 

Reflection

Reflection is the process in which a part of the incoming solar radiation bounces back into space without being absorbed.

Examples:

• Clouds reflect a large amount of sunlight.
• Snow and ice reflect most of the incoming radiation.
• Desert sand also reflects considerable sunlight.

Absorption

Absorption is the process by which the Earth's surface and atmosphere absorb solar energy and convert it into heat.

• Land and water absorb solar energy.
• The atmosphere absorbs part of the incoming radiation.
• Absorbed energy increases the Earth's temperature.

Scattering

Scattering is the process in which atmospheric gases, dust particles and water droplets redirect solar radiation in different directions.

• Makes the sky appear blue.
• Produces colourful sunrise and sunset.
• Distributes sunlight throughout the atmosphere.

Albedo

Albedo is the fraction or percentage of incoming solar radiation reflected by a surface without being absorbed. Different surfaces have different albedo values. 

Surfaces with Different Albedo

Importance of Albedo

• Controls the Earth's energy balance.
• Influences surface temperature.
• Affects weather and climate.
• Helps regulate global heat distribution.

Uneven Heating of the Earth

The Earth does not receive equal amounts of solar energy everywhere. Different regions receive different amounts of insolation because of the Earth's shape, tilt and atmospheric conditions. 

Causes of Uneven Heating

• The Earth is spherical.
• Sun's rays strike different places at different angles.
• The Earth's axis is tilted.
• Day length changes with seasons.
• Cloud cover and atmospheric conditions vary.
• Land and water heat at different rates.

Effects of Uneven Heating

• Formation of pressure belts.
• Development of winds.
• Formation of ocean currents.
• Seasonal changes.
• Differences in climate across the world.

Key Terms at a Glance

Our Concept Builder

The Earth's climate depends on the balance between incoming and outgoing solar radiation. Reflection, absorption and scattering determine how much solar energy is available to heat the Earth, while differences in albedo and uneven heating create variations in temperature, winds and climate across the globe. 

Our Exam Booster

• Remember the definitions of reflection, absorption, scattering and albedo.
• Know which surfaces have high and low albedo.
• Understand why snow-covered regions remain cooler than forests or oceans.
• Learn the causes and effects of uneven heating of the Earth.
• Remember that unequal heating is responsible for winds, ocean currents and seasonal changes.
• CBSE competency-based questions may ask students to explain how albedo influences Earth's climate or why different regions receive different amounts of solar energy.