Radiation
1. Radiation (Physics)
What is Radiation?
Radiation is the transfer of energy from one place to another without the need for a material medium. Energy travels in the form of electromagnetic waves or particles.
Radiation can travel through:
Vacuum (empty space)
Air
Transparent materials
That’s why heat from the Sun reaches Earth.
Types of Radiation
1. Electromagnetic Radiation
Does not need particles or a medium.
Examples (from low to high energy):
Radio waves
Microwaves
Infrared (heat radiation)
Visible light
Ultraviolet
X-rays
Gamma rays
2. Particle Radiation
Consists of fast-moving particles.
Alpha particles
Beta particles
Neutrons
Used in nuclear reactions and medical treatments.
Properties of Radiation
Travels in straight lines
Moves at the speed of light (≈ 3 × 10⁸ m/s)
Can be absorbed, reflected, or transmitted
Intensity decreases with distance
Examples of Radiation in Daily Life
Heat felt near a fire
Sunlight
X-ray imaging
Microwave ovens
2. Energy from the Sun (Solar Energy)
What is Solar Energy?
Solar energy is energy received from the Sun in the form of radiation.
The Sun produces energy through nuclear fusion, where hydrogen atoms combine to form helium, releasing huge amounts of energy.
How Solar Energy Reaches Earth
Energy is emitted as electromagnetic radiation
Travels through the vacuum of space
Reaches Earth as heat and light
Forms of Solar Energy
Light energy – helps plants grow (photosynthesis)
Heat energy – warms Earth
Electrical energy – produced using solar panels
Uses of Solar Energy
Solar panels (electricity)
Solar cookers
Solar heaters
Drying clothes and crops
Supporting life on Earth
Advantages of Solar Energy
Renewable and unlimited
Non-polluting
Reduces electricity bills
Sustainable energy source
Disadvantages of Solar Energy
Depends on weather and daylight
Expensive initial setup
Needs large area for panels
Energy storage is difficult
3. Good and Bad Radiators
What is a Radiator?
A radiator is a surface or object that emits heat energy in the form of radiation.
Good Radiators
Good radiators emit heat efficiently.
Characteristics:
Dull
Black
Rough surfaces
Examples:
Blackened metal surfaces
Matte black paint
Car radiators (dark colored)
Bad Radiators
Bad radiators emit very little heat.
Characteristics:
Shiny
Polished
Smooth surfaces
Examples:
Silvered surfaces
Polished metal
Mirrors