For any given (photo)chemical system, a molar balance can be derived, as illustrated in Equation using an exemplary chemical actinometry batch experiment under ideal conditions. In this context, the rate at which the number of moles of species 𝑖𝑖 changes over time (𝑑𝑑𝑁𝑁 𝑖𝑖 /𝑑𝑑𝑑𝑑) is governed by the photon flux reaching the medium (𝑞𝑞 𝑛𝑛,𝑝𝑝 ). This is further influenced by the light absorbed by the attenuating species 𝑖𝑖, represented as the fraction of light that the system does not transmit (1 -𝑇𝑇), and the known quantum yield of the reaction (𝜑𝜑).