DP Physics (last assessment 2024)

Question 18N.2.SL.TZ0.6

Date	November 2018	Marks available	[Maximum mark: 6]	Reference code	18N.2.SL.TZ0.6
Level	SL	Paper	2	Time zone	TZ0
Command term	Determine, Outline, Show that	Question number	6	Adapted from	N/A

[Maximum mark: 6]

18N.2.SL.TZ0.6

The ratio $\frac{{{\text{distance of Mars from the Sun}}}}{{{\text{distance of Earth from the Sun}}}}$ = 1.5.

(a)

Show that the intensity of solar radiation at the orbit of Mars is about 600 W m^–2.

[2]

Markscheme

use of $I \propto \frac{1}{{{r^2}}}$ «1.36 × 10³ × $\frac{1}{{{{1.5}^2}}}$ » ✔

604 «W m^–2» ✔

(b)

Determine, in K, the mean surface temperature of Mars. Assume that Mars acts as a black body.

[2]

Markscheme

use of $\frac{{600}}{4}$ for mean intensity ✔

temperature/K = « $\sqrt[4]{{\frac{{600}}{{4 \times 5.67 \times {{10}^{ - 8}}}}}} =$ » 230 ✔

(c)

The atmosphere of Mars is composed mainly of carbon dioxide and has a pressure less than 1 % of that on the Earth. Outline why the greenhouse effect is not significant on Mars.

[2]

Markscheme

recognize the link between molecular density/concentration and pressure ✔

low pressure means too few molecules to produce a significant heating effect

low pressure means too little radiation re-radiated back to Mars ✔

Syllabus sections

Core

Core » Topic 8: Energy production » 8.2 – Thermal energy transfer

Core » Topic 4: Waves » 4.3 – Wave characteristics

Core » Topic 4: Waves

Core » Topic 8: Energy production

Question 18N.2.SL.TZ0.6

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