Past exam of the mathematics course of the University of Cambridge / 2019 / iii / Paper 338 / 1 / c / i

The magnitude zero point is defined by the reference response $I_0$. With zero magnitude assigned to that reference, the apparent magnitude isThe two responses must use the same photometric passband and instrumental weighting. If the reference has assigned magnitude $m_0$ instead, add $m_0$ to the right-hand side.