COSMIC MICROWAVE BACKGROUND (CMB) RADIATION

3 marks · Normal

Light from a distant galaxy shows an absorption line at a wavelength of 650 nm, while the same line from our Sun is at 520 nm. Calculate the speed at which the galaxy is moving relative to Earth. (Speed of light = )

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7.5 \times 10^7\ \mathrm{m/s} m/s (±2000000)

Also accept: 7.50 \times 10^7 m/s

Common mistakes: incorrect substitution of wavelengths; inverted fractions

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Marking points

M1 · 1 mark · Substitutes values into correctly. (follow-through)

A1 · 1 mark · Accurately calculates nm and nm. (follow-through)

A2 · 1 mark · Final answer in standard form with unit (m/s).

Worked solution