Solution

ID: past-exam-of-the-short-options-paper-shared-by-prelims-and-parts-a-and-b-of-the-physics-course-of-the-university-of-oxford/2016/s2/3/1/solution

Expansion redshifts photon energies and preserves a blackbody spectrum, so a comoving observer at sees K. A one-sided dipole excess of 0.105% means , hence . Motion is toward the hotter region. The peak-to-peak contrast is twice this, so using 0.210% for would double the inferred speed incorrectly.

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