Ablack 4 cm x 8 cm sheet of metal is heated uniformly with 1000 watts by passing an electric current through it. one face of the rectangle is well insulated. the other face is exposed to vacuum and very cold surroundings. at thermal equilibrium what fraction of the emitted energy is in the wave number range of 0.5 to 2 μm-1 ?

On solidification from a melt, the polymer polyethylene forms a semi-crystalline spherulite structure. (i) sketch an individual spherulite and label the amorphous and crystalline regions. (ii) draw a schematic to show the changes in specific volume with temperature during cooling from the melt, comparing it to the theoretical extremes of fully crystalline and fully amorphous (indicate tm and tg)