Absorption: Earth absorbs radiation from the Sun (mainly visible and short-wave IR)
Emission: Earth emits radiation back to space (longer-wave infrared — because Earth is cooler than Sun)
Equilibrium: Earth's temperature is stable when:
Greenhouse effect:
- Greenhouse gases (CO₂, CH₄, H₂O) absorb outgoing infrared radiation
- They re-emit it in all directions — some back to Earth
- This reduces the rate of energy loss to space
- Earth must warm up until emission rate matches absorption again
- More greenhouse gases → higher equilibrium temperature → global warming
This key facts covers Earth's Temperature Balance within Black Body Radiation for GCSE Physics. Revise Black Body Radiation in Energy for GCSE Physics with 16 exam-style questions and 5 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 4 of 7 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Black Body Radiation
What is a perfect black body?
Explain how the radiation emitted by an object changes as its temperature increases.