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GCSE Physics · key term
The energy carried by radiation through a unit area each second; greater intensity means a greater rate of energy transfer.
Used by AQA, Edexcel and OCR
Specification 4.6.3.2 · Paper 2
The rate at which radiation transfers energy per unit area, measured in watts per square metre (W/m²).
Revise: Perfect black bodies and radiationHeating an object increases the intensity of its emission: it transfers more energy by radiation each second from each square metre of its surface.
Specification 5.15P, 5.21 · Paper 1
The power of radiation emitted per unit area; greater intensity means more energy is emitted each second from the same area.
Revise: Emission and TemperatureA graph of intensity against wavelength shows how strongly it emits at each wavelength. The highest point is the peak wavelength: the wavelength at which emission is most intense.
The amount of energy transferred by radiation each second to each unit area; more intense radiation can transfer energy more rapidly.
Specification P8.3d · Paper 2 (Foundation), Paper 4 (Higher)
Revise: Radiation emissionA hotter body emits radiation with greater intensity, transferring more energy by radiation in a given time.
Paper 1, Paper 2
The power of radiation passing through or arriving at each unit area.
Revise: Climate change and evidenceA body emits a range, or distribution, of wavelengths rather than one single wavelength. Its temperature determines both the intensity of this emission and how the emitted energy is distributed across those wavelengths.
When comparing emission curves, describe both the greater intensity and the shift of the peak towards shorter wavelengths at higher temperature.
Do not claim that frequency alone determines the actual harm in every exposure. Exposure time and intensity also matter.
Do not say simply that a hotter body emits ‘more heat’. State that it emits electromagnetic radiation at greater intensity and that its wavelength distribution shifts towards shorter wavelengths, with a higher principal frequency.
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