This key facts covers RADIATION — Heat Without Particles within Heat Transfer for GCSE Physics. Revise Heat Transfer in Energy for GCSE Physics with 14 exam-style questions and 11 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 5 of 17 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
☀️ RADIATION — Heat Without Particles
What it is: Transfer of energy by infrared (IR) waves — part of the electromagnetic spectrum.
Key facts:
- Does NOT need particles — works through a vacuum
- This is how the Sun heats the Earth (through space)
- ALL objects emit AND absorb infrared radiation
- Hotter objects emit MORE infrared radiation
- Travels at the speed of light
Surfaces and radiation:
| Surface | Absorbs IR | Emits IR | Reflects IR |
|---|---|---|---|
| Matt black | BEST absorber | BEST emitter | Poor reflector |
| Shiny silver/white | Poor absorber | Poor emitter | BEST reflector |
Examples:
- Black car in sun — absorbs more IR → gets hotter inside
- White/silver car — reflects more IR → stays cooler
- Rescue blankets (shiny) — reflect body heat back to keep you warm
Practice questions for Heat Transfer
Which method of thermal energy transfer occurs mainly in solids?
Explain how a convection current forms when the base of a fluid is heated.
Quick recall flashcards
Examples
wood, plastic, glass, air, wool
Fluid is heated
particles gain kinetic energy → move faster → spread out