Solar Energy on Earth Chapter Notes | Science for Grade 6 PDF Download

Introduction

The Sun is a giant source of energy that helps keep Earth warm and supports life. In this chapter, we will learn how energy from the Sun reaches Earth, how it affects different surfaces like land and water, and why some places on Earth are warmer than others. We will also explore how the color of surfaces impacts how much solar energy they absorb and how this energy influences the air around us. By understanding these ideas, we can see how the Sun plays a big role in Earth's weather and climate.

How does energy from the Sun reach Earth?

• The Sun sends energy to Earth through a process called radiation.
• Radiation is when thermal energy travels as electromagnetic waves.
• All things, like the Sun, fire, or even ice, give off thermal energy through radiation.
• Thermal energy moves from hotter areas to cooler areas.
• Radiation does not need air or water to travel; it can move through empty space.
• This is why the Sun's energy can reach Earth from far away in space.
• You can feel radiation when you hold your hands near a fire and feel the warmth.

Why is Earth warmer at the equator and colder at the poles?

• The Sun's energy does not reach all parts of Earth equally.
• The equator gets more direct sunlight, making it warmer.
• At the poles, sunlight hits at a low angle, spreading over a larger area, so it is colder.
• Latitude is the distance in degrees north or south of the equator.
• Near the equator (tropics), sunlight hits almost straight (90° angle) all year, giving more energy per area.
• At the poles, sunlight hits at a low angle, spreading energy over a bigger area, so less energy reaches each spot.
• This difference in sunlight angle causes warmer temperatures at the equator and colder temperatures at the poles.

What happens to solar radiation on Earth?

• When sunlight reaches Earth, it turns into thermal energy.
• Different surfaces, like land and water, absorb and release this energy differently.
• Water absorbs and releases heat more slowly than land because it has a high specific heat.
• Specific heat is the amount of energy needed to raise the temperature of 1 kg of a material by 1°C.
• Water’s specific heat is about six times higher than land’s, so land heats up and cools down faster.

How do surfaces on Earth affect the atmosphere?

• Land and water affect the temperature of the air above them.
• Air has a lower specific heat than land or water, so it heats up and cools down faster.
• When land or water gets warm, it can heat the air above it through a process called conduction.
• Conduction is when thermal energy moves from one object to another through direct contact.
  • In conduction, energy moves from warmer objects (like land or water) to cooler objects (like air).
  • Conduction happens when particles with more energy bump into particles with less energy, transferring heat.
• This process warms the air just above the ground or water.
• When light passes through this warm air layer, it can bend, creating a mirage.

How does the color of a surface affect how solar energy is absorbed?

• The color of a surface affects how much solar energy it absorbs or reflects.
• Albedo is a measure of how reflective a surface is.
• Light-colored surfaces, like ice or clouds, have high albedo and reflect more sunlight.
• Dark surfaces, like soil or water, have low albedo and absorb more sunlight.
• Surfaces with high albedo (like ice) keep areas cooler because they reflect sunlight.
• Surfaces with low albedo (like dark soil) make areas warmer because they absorb more sunlight.
• The albedo of Earth’s surfaces (land, water, plants) affects the temperature of the atmosphere.

Did You Know?

Plants absorb some solar energy and turn it into chemical energy (sugars) to grow.

A Closer Look: Monitoring Earth's Albedo

• Satellites like NASA’s Terra and Aqua use an instrument called MODIS to measure Earth’s albedo every day.
• Terra and Aqua satellites orbit Earth, one in the morning and one in the afternoon, to collect data on the whole surface every 1-2 days.
• This data helps create images of changes in land ice coverage with seasons.
• Albedo data helps scientists predict weather and climate changes.
• Snow and ice reflect more sunlight than land or water, keeping Earth cooler.
• If snow or ice melts, more sunlight is absorbed, making Earth warmer.
• Monitoring albedo helps scientists understand how changes in ice affect Earth’s temperature.