A student heats a bar of chocolate in the microwave for one minute. When they remove the bar they observe that there are patches of melted chocolate with unmelted chocolate between them. Suggest the mechanism of how this happens.

This question is about standing waves, the bar of chocolate melts only in the positions where antinodes are formed on the standing wave as they transfer the most energy as they have the greatest amplitude of vibration, the unmelted parts are where nodes were formed along the standing wave, points of zero amplitude.