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Question 20N.3.HL.TZ0.21c

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Date November 2020 Marks available [Maximum mark: 3] Reference code 20N.3.HL.TZ0.21c
Level HL Paper 3 Time zone TZ0
Command term Explain Question number c Adapted from N/A
c.
[Maximum mark: 3]
20N.3.HL.TZ0.21c
(c)

Hubble originally linked galactic redshift to a Doppler effect arising from galactic recession. Hubble’s law is now regarded as being due to cosmological redshift, not the Doppler effect. Explain the observed galactic redshift in cosmological terms.

[3]

Markscheme

reference to «redshift due to» expansion of the universe, «not recessional speed» ✓

expansion of universe stretches spacetime / increases distance between objects ✓

«so» wavelength stretches / increases leading to observed redshift ✓

Examiners report

The galactic redshift was successfully explained by many in terms of the stretching of spacetime.

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