The space between two large horizontally placed plates at distance $l$ from each other is filled with air. The temperature of the lower and upper plate is kept equal to $T_1$ and $T_2$.

Considering air to be an ideal gas, determine at what temperature difference $\Delta T = T_1 - T_2$ in the system convection occurs.

Heat transfer between adjacent layers of air during convection can be neglected. In the absence of convection, the temperature changes linearly with height. Consider the molar heat capacity of air at constant volume $C_v$ and its molar mass $\mu$ as known.