1.1. Fig. 2.1 shows a hollow metal cube filled with boiling water. The temperature of the four vertical surfaces are equal but each surface has a different colour or texture.

Fig. 2.1

A thermal radiation sensor is placed the same distance from each surface and the meter reading measures the thermal radiation emitted from each surface. 

The results are shown in Fig. 2.2.

Draw a line linking each type of surface with the appropriate meter reading. One line has been drawn for you.

Fig. 2.2

1.2. The hot surfaces produce a convection current in the air outside the metal cube.

Describe how the convection current is produced.