THE DOPPLER EFFECT
3 marks · NormalA sodium lamp on Earth emits a spectral line with a wavelength of 589 nm. The same line from a distant galaxy is observed at 600 nm.
Calculate the red-shift () of light from this galaxy. Use:\n\[ z = \frac{\Delta \lambda}{\lambda_0} \] where is the original wavelength.
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z = 0.019 (±0.001)
Common mistakes: Incorrect formula rearrangement; Forgetting to use correct lambda
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Marking points
M1 · 1 mark · Writes or quotes red-shift equation: z = (λ_observed - λ_0) / λ_0 or equivalent.
M1 · 1 mark · Substitutes correct values: (600 - 589)/589
A1 · 1 mark · Correct value obtained: z = 0.019 (accept 0.0190 or values rounding within tolerance).
Worked solution
Δλ = 600 nm - 589 nm = 11 nm