IB Physics HL B.1.16 Luminosity and brightness Question Bank

Practise IB Physics HL B.1.16 by linking luminosity, apparent brightness, magnitude and distance methods such as standard candles and Cepheids.

Exam points

Rearrange b=L/(4πd²) to determine luminosity or distance from apparent brightness data.
Use magnitude scales, Cepheids and type Ia supernovae as standard candles to estimate galaxy distances.

[Maximum number: 2]

The diagram shows a simplified energy-balance model for the Earth surface-atmosphere system.

Figure for Question B.1.16—Luminosity and brightness question 1 — IB Physics HL

The following data are given:

\begin{aligned} \text { Average albedo of Earth } & =0.30 \\ \text { Average global temperature of the surface } & =288 \mathrm{~K} \\ \text { Average Earth-Sun distance } & =1.5 \times 10^{11} \mathrm{~m} \end{aligned}

Show, with reference to the solar constant, that the total power radiated by the Sun is about $4 \times 10^{26} \mathrm{~W}$ .

Recognition that $r=1.5 \times 10^{11} m$ AND $S=1.36 \times 10^{3} \mathrm{~W} \mathrm{~m}^{-2}$ $4 \pi\left(1.5 \times 10^{11}\right)^{2} \times 1.36 \times 10^{3}$ or $3.8 \times 10^{26} \mathrm{~W}$

Unit is not required.

The values of r and S must be seen to award MP1.

Marking guidance:

Allow ECF from use of
$S=1.4 \times 10^{3} \mathrm{Wm}^{-2}$

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B.1.16—Luminosity and brightness question 1