2024HSCShort answer

Q22 (b)

3 marks

Question

The following graph, based on the data gathered by Hubble, shows the relationship between the recessional velocity of galaxies and their distance from Earth.
How were the recessional velocities of galaxies determined?

Try the question before revealing the answer.

Solution

Criteria	Marks
Demonstrates understanding of how the recessional velocities of galaxies were determined	3
Outlines some aspects of determination of recessional velocities of galaxies	2
Provides some relevant information	1

Sample answer: The spectra of the galaxies were compared to the spectra of hydrogen. The degree of red-shift of the galaxies was determined. The larger the red-shift is, the greater recessional velocity of the light source, hence the velocities of the galaxies were able to be determined.

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Syllabus alignment

Module 8 · From the Universe to the Atom

Origins of the ElementsAnalyse Big Bang evidence, Hubble's observations and expansion of the universe.

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