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Question 19M.3.HL.TZ2.a

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Date May 2019 Marks available [Maximum mark: 3] Reference code 19M.3.HL.TZ2.a
Level HL Paper 3 Time zone TZ2
Command term Explain Question number a Adapted from N/A
a.
[Maximum mark: 3]
19M.3.HL.TZ2.a

A rocket is accelerating upwards at 9.8 m s-2 in deep space. A photon of energy 14.4 keV is emitted upwards from the bottom of the rocket and travels to a detector in the tip of the rocket 52.0 m above.

Explain why a change in frequency is expected for the photon detected at the top of the rocket.

[3]

Markscheme

ALTERNATIVE 1

detector accelerates/moves away from point of photon emission ✔

so Doppler effect / redshift ✔

so f decreases ✔

ALTERNATIVE 2

equivalent to stationary rocket on earth’s surface ✔

photons lose «gravitational» energy as they move upwards ✔

h f OR f decreases ✔

Examiners report

Most candidates answered this question correctly using the equivalence principle and could show that the frequency would decrease.

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