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Date May 2018 Marks available 2 Reference code 18M.3.HL.TZ1.7
Level Higher level Paper Paper 3 Time zone 1
Command term Calculate Question number 7 Adapted from N/A

Question

An observer A is on the surface of planet X. Observer B is in a stationary spaceship above the surface of planet X.

Observer A sends a beam of light with a frequency 500 THz towards observer B. When observer B receives the light he observes that the frequency has changed by Δf.

M18/4/PHYSI/HP3/ENG/TZ1/07_01

Observer B then sends a signal with frequency 1500 THz towards observer A.

M18/4/PHYSI/HP3/ENG/TZ1/07_02

Calculate the shift in frequency observed by A in terms of Δf.

[2]
a.

Calculate the gravitational field strength on the surface of planet X.

                                    The following data is given:

                                    Δf = 170 Hz.

The distance between observer A and B is 10 km. 

[2]
b.

Observer A now sends a beam of light initially parallel to the surface of the planet.

M18/4/PHYSI/HP3/ENG/TZ1/07.c

Explain why the path of the light is curved.

[2]
c.

Markscheme

Δf   f

therefore the change is «»f

[2 marks]

a.

g«c2  Δ f f Δ h =» (3 × 108)2 170 5.0 × 10 14 × 10 000

g = 3.1 «ms–2»

 

If POT mistake, award [0].

Award [2] for BCA.

[2 marks]

b.

the mass of the planet warps spacetime around itself

the light will follow the shortest path in spacetime «which is curved»

[2 marks]

c.

Examiners report

[N/A]
a.
[N/A]
b.
[N/A]
c.

Syllabus sections

Option A: Relativity » Option A: Relativity (Additional higher level option topics) » A.5 – General relativity (HL only)
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Option A: Relativity » Option A: Relativity (Additional higher level option topics)
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