Where the heat goes.

Model assumptions

Steady state, with ambient at 24.5 °C and still air over the open surfaces. The objective is a simplified solid held at 24.5 °C at its thread, so it acts as a heat sink. Immersion oil is 0.28 mm between coverslip and objective. The sample is 100 µm of water; no fluid motion is modelled, so the sample and the surrounding air gap are solved as conductors. Conductivities are constant, with no temperature dependence. Every interface is treated as perfect thermal contact.