An automated observatory compares three absorption lines recorded from one galaxy with their laboratory wavelengths.
| absorption line | laboratory wavelength in nm | observed wavelength in nm |
|---|---|---|
| P | 450 | 468 |
| Q | 550 | 572 |
| R | 650 | 637 |
The observatory reports that all three lines show that the galaxy is moving away from the Earth.
Calculate the percentage increase in wavelength for absorption line P.
Evaluate the observatory's interpretation.
Use the data in the table and your answer to (a).
A reference galaxy has a confirmed percentage increase in wavelength of 1.0% and is 1.3 × 1024 m from the Earth.
The distance to a galaxy is approximately proportional to its percentage increase in wavelength.
Using only the consistent red-shifted measurements in the table, calculate the predicted distance to the galaxy.
94 exam-style questions on Edexcel GCSE Physics 7.2 The Universe and red-shift, covering 7.2.1 Big Bang and Steady State theories, 7.2.2 Evidence for the Big Bang, 7.2.3 The Doppler effect and red-shift, 7.2.4 Red-shift as evidence for an expanding Universe, and 7.2.5 The CMB and the accepted model. Each one has a worked solution and a mark scheme showing where the marks go.