CAPE Physics Unit 1 · 2006 · Paper 2 · Question 8(c)(i)

The rate, P, at which an object radiates energy, is proportional to the fourth power of the absolute temperature, T. The intensity of the radiation a distance, r, from the source is given by I = P/(4πr²). These relationships may be investigated by using a thermopile connected to a micro-voltmeter and exposing it to the radiation from a small heated sphere that radiates as a point source. Table 3 shows the micro-voltmeter readings, V, obtained when the sphere was maintained at various temperatures and the thermopile was a distance r from it. The voltage, V, of the thermopile is proportional to the intensity of radiation falling on it.

Suggest how the intensity of radiation reaching the thermopile varies with the absolute temperature, T, of the sphere.

This question uses a figure or table from the paper — you'll see it when you practise.