AQA GCSE Physics
AQA GCSE Physics 4.6.3 Black Body Radiation Exam Questions
Free AQA GCSE Physics exam questions for 4.6.3 Black Body Radiation, with a mark scheme for every pack. Covers emission and absorption of infrared radiation, temperature and intensity, perfect black bodies, and the Earth's temperature balance.
4.6.3 Black Body Radiation exam questions
1 question pack of real past exam questions, each with its mark scheme. Do not stop after a few: answer as many as you can without notes, then mark every answer with the mark scheme. The more questions you do, the more quickly you will spot how examiners ask about each idea.
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About AQA GCSE Physics 4.6.3 Black Body Radiation
Black body radiation is a physics only section of AQA GCSE Physics, examined on Paper 2. It explains that all bodies emit and absorb infrared radiation, and that hotter bodies emit more radiation per second and at shorter wavelengths. You need to define a perfect black body and explain what happens when an object's temperature is constant, rising or falling. Higher tier only content covers the factors affecting the temperature of the Earth. Examiners test explanations involving the balance between absorbed and emitted radiation.
What you need to know
- All bodies emit radiation All bodies (objects), no matter what temperature, emit and absorb infrared radiation. The hotter the body, the more infrared radiation it radiates in a given time.
- Perfect black body A perfect black body is an object that absorbs all of the radiation incident on it. A black body does not reflect or transmit any radiation. Since a good absorber is also a good emitter, a perfect black body would be the best possible emitter.
- Temperature and intensity All bodies emit radiation. The intensity and wavelength distribution of any emission depends on the temperature of the body. As temperature increases, intensity increases and the peak shifts to shorter wavelengths.
- Constant temperature A body at constant temperature is absorbing radiation at the same rate as it is emitting radiation. If it absorbs faster than it emits, its temperature increases; if it emits faster, its temperature decreases.
- Earth's temperature (Higher tier only) The temperature of the Earth depends on many factors including the rates of absorption and emission of radiation and reflection of radiation into space. Explain this using diagrams showing radiation from the Sun absorbed, reflected and re-emitted.
Common mistakes in 4.6.3 Black Body Radiation
- Saying only hot objects emit infrared. All objects emit infrared radiation, whatever their temperature.
- Saying an object at constant temperature has stopped absorbing or emitting. It is absorbing and emitting at the same rate.
- Saying a perfect black body is black because it has no radiation. It absorbs all incident radiation and is the best emitter.
- Saying hotter objects emit longer wavelengths. Hotter objects emit more radiation with a peak at shorter wavelengths.
Try three 4.6.3 Black Body Radiation exam-style questions
1. Define a perfect black body. (2 marks)
Show the mark scheme answer
An object that absorbs all of the radiation incident on it; it does not reflect or transmit any radiation.
2. A mug of tea is left on a table and its temperature stops changing. Explain this in terms of radiation. (2 marks)
Show the mark scheme answer
The mug is absorbing radiation at the same rate as it emits radiation; so there is no net energy transfer and the temperature is constant.
3. Higher tier: Explain how the Earth's temperature remains roughly constant. (4 marks)
Show the mark scheme answer
The Earth absorbs radiation from the Sun; some radiation is reflected back into space (by clouds, ice and the atmosphere); the Earth emits infrared radiation; when the rate of absorption equals the rate of emission the temperature stays constant (changes to the atmosphere that reduce emission to space cause the temperature to rise).
4.6.3 Black Body Radiation FAQs
What does AQA GCSE Physics 4.6.3 Black body radiation cover?
It covers how all bodies emit and absorb infrared radiation, perfect black bodies, how temperature affects emission and, for Higher tier, the Earth's temperature balance.
Is black body radiation on Combined Science?
No. Black body radiation is physics only, so it is only on the separate AQA GCSE Physics Paper 2.
What is the key idea for black body explanations?
Compare the rate of absorption with the rate of emission: equal rates give constant temperature, absorbing faster means warming, emitting faster means cooling.
