Earlier today I set you a puzzle about keeping homes cool in a heatwave. Here it is again with the solution.
Imagine a room with a set of curtains. When the Sun is shining, its energy comes through the windows where it is absorbed by the curtains. The curtains get hotter and hotter until they reach a temperature at which they are radiating as much heat as they absorb. The curtains radiate 50 per cent of this heat back towards the window, and 50 per cent of the heat into the room.
