Frequently Examined
This topic is examined in Edexcel 1PH0/1 (Paper 1). Edexcel questions often present a data set — such as radiation spectra for two stars or the Earth — and ask you to compare temperatures using peak wavelength, or to explain the greenhouse effect mechanism in a given context. Expect "Suggest" and "Explain" command words worth 3–4 marks. Common question types:
- Define a black body (2 marks) — must name both properties: perfect absorber AND perfect emitter
- Describe how radiation emitted changes with temperature (3 marks) — total increases, peak wavelength decreases, peak frequency increases
- Explain the greenhouse effect (4 marks) — absorption, re-emission in all directions, less escaping to space, temperature rise to new equilibrium
- Compare two objects using peak wavelength data (2 marks) — shorter peak wavelength = higher temperature
- Radiation balance / Earth's temperature (3 marks) — absorbed solar = emitted infrared at stable temperature
The most common mistake: saying greenhouse gases "block" incoming sunlight. They absorb the infrared radiation emitted by the Earth, not the incoming solar radiation.
This exam focus covers Exam Focus 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 5 of 7 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
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.