Edexcel A-Level Physics Radiation Intensity and Luminosity

Review radiation intensity in Edexcel A-Level Physics through luminosity-distance calculations, inverse-square graphs and star or lamp data.

Exam points

calculate intensity, luminosity or distance using I = L/(4πd²) and astronomical data
compare received intensities using luminosity ratios and inverse-square distance scaling
interpret I against distance or 1/d² graphs for lamp and light-meter practical contexts

[Maximum number: 2]

Cepheid variable stars are used by astronomers as standard candles.

The luminosity of Cepheid variable stars varies periodically.

There is a linear relationship between the period and the mean luminosity of a Cepheid variable star, as shown.

Figure for Question 5.6.164 - Radiation intensity from luminosity and distance question 1 — Edexcel A-Level Physics A2

When viewed from Earth, the mean intensity of this Cepheid variable star is 5.1 × 10^-4 W m^-2.

Determine the distance of this Cepheid variable star from Earth.

Distance of this Cepheid variable star from Earth =

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5.6.164 - Radiation intensity from luminosity and distance question 1