DP Physics (first assessment 2025)

Question 20N.2.SL.TZ0.15a

Date	November 2020	Marks available	[Maximum mark: 1]	Reference code	20N.2.SL.TZ0.15a
Level	SL	Paper	2	Time zone	TZ0
Command term	Show that	Question number	a	Adapted from	N/A

[Maximum mark: 1]

20N.2.SL.TZ0.15a

(a)

Show that the apparent brightness $b \propto \frac{A T^{4}}{d^{2}}$ , where $d$ is the distance of the object from Earth, $T$ is the surface temperature of the object and $A$ is the surface area of the object.

[1]

Markscheme

substitution of $L = σ A T^{4}$ into $b = \frac{L}{4 {πd}^{2}}$ giving $b = \frac{σ A T^{4}}{4 {πd}^{2}}$

Removal of constants $σ$ and $4 π$ is optional

Syllabus sections

E. Nuclear and quantum physics » E.5 Fusion and stars

Question 20N.2.SL.TZ0.15a

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Syllabus sections

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