Earth as a System | Class 9 Science Notes
By ConceptScroll Team · Published on 17 July 2026 · 3 min read
Earth as a System – this guide gives you a concise, exam-ready overview of Earth as a System from Class 9 Science, written by ConceptScroll editors and reviewed against the latest NCERT textbook.
13.1 Uneven Heating of the Earth
Solar radiation is the primary source of energy for Earth, arriving as electromagnetic (EM) waves traveling at the speed of light (3 × 10⁸ m/s) through the vacuum of space. The electromagnetic spectrum includes a wide range of wavelengths and frequencies, from high-energy gamma rays and X-rays to low-energy infrared and radio waves. However, the Sun's radiation reaching Earth is mainly concentrated in the ultraviolet (UV), visible, and infrared (IR) regions, which together account for about 99% of solar energy. High-energy gamma rays and X-rays are mostly absorbed by Earth's upper atmosphere, protecting life from their harmful effects. UV radiation is largely absorbed by the ozone layer, which shields living organisms from damage. Visible light reaches Earth's surface and drives photosynthesis, the foundation of most food chains. Infrared radiation warms the Earth's surface, which then re-radiates heat back into the atmosphere. Greenhouse gases like carbon dioxide (CO₂), methane (CH₄), and water vapor trap some of this heat, maintaining Earth's temperature suitable for life. The amount of solar energy received per unit area at the top of Earth's atmosphere is called the solar constant, approximately 1.4 kW/m² (1400 J/s/m²). However, due to absorption and scattering by atmospheric gases, clouds, and dust, the maximum solar energy reaching Earth's surface under clear skies is about 1 kW/m². India's tropical location results in abundant sunlight year-round, supporting its climate and agriculture and offering great potential for solar energy utilization.
📊 Diagram: Fig. 13.2: Electromagnetic spectrum showing different types of radiation; Fig. 13.3: Solar Radiation Over India by Anna Mani and S. Rangarajan; Fig. 13.4: Solar panel in the desert illustrating solar energy harnessing.
🧪 Activity: Activity 13.2: Find albedo values of common materials from authentic sources to understand reflection of solar radiation.
🔗 Connection: This section leads to understanding how solar radiation interacts with Earth's surface and atmosphere, causing uneven heating that drives winds and ocean currents.
Frequently asked questions
Identify and explain the five main spheres of the Earth system and give one example of each.
The five main spheres of the Earth system are: 1. Geosphere: solid rocks, soil, landforms (e.g., Deccan plateau). 2. Hydrosphere: all liquid water like oceans and rivers (e.g., Ganga–Brahmaputra river system). 3. Cryosphere: solid water such as glaciers and polar ice caps (e.g., Himalayan glaciers). 4. Atmosphere: the layer of gases surrounding Earth (e.g., air in forests). 5. Biosphere: all living organisms and their habitats (e.g., mangroves). These spheres interact continuously to support lif
Fig. 13.1 shows features of the Earth's surface including mountains, lakes, snow, air, and vegetation. Identify which feature represents the cryosphere and explain how snow from the cryosphere can become part of a lake in the hydrosphere.
The snow-covered mountains represent the cryosphere. Snow melts due to temperature rise and the meltwater flows downhill, eventually feeding into lakes, which are part of the hydrosphere.
How does warming of Arabian Sea water affect the southwest monsoon in India?
Warming of Arabian Sea water increases evaporation, leading to more moisture in the atmosphere. This causes fluctuations in the southwest monsoon, resulting in variable rainfall patterns, including floods in some regions and droughts in others.
What is the solar constant, and what is its approximate value? Why is it important for understanding Earth's climate?
The solar constant is the average amount of solar energy received per unit time per unit area perpendicular to the Sun's rays at the top of Earth's atmosphere. Its value is about 1.4 kilowatts per square metre (1.4 kW/m²). It is important because it represents the energy input that drives Earth's climate and weather systems.
Ready to ace this chapter?
Get the full Earth as a System chapter — interactive notes, diagrams, worked solutions, polls and a free practice quiz — in the ConceptScroll app.
Study smarter with ConceptScroll
Daily NCERT-aligned reels, AI doubt solving and chapter quizzes — all free.
Start learning freeContinue reading
- खाद्य संसाधनों में सुधार | Class 9 Science Notes
Clear NCERT-aligned notes on खाद्य संसाधनों में सुधार for Class 9 Science.
- खाद्य संसाधनों में सुधार | Class 9 Science Notes
Clear NCERT-aligned notes on खाद्य संसाधनों में सुधार for Class 9 Science.
- खाद्य संसाधनों में सुधार | Class 9 Science Notes
Clear NCERT-aligned notes on खाद्य संसाधनों में सुधार for Class 9 Science.