A microwave oven sends electromagnetic waves into food. Water and other molecules in the food interact with the changing electric field and energy is transferred into the food's thermal energy store. Many plates are designed from materials that absorb microwaves less strongly than food does. They therefore receive less energy directly from the waves. The plate can still become hot because it is touching hot food, so thermal energy transfers by conduction from the food into the plate. Different materials absorb microwaves differently, which is why some containers stay relatively cool while others become very hot.

The effect becomes easier to notice when conditions change. Temperature, pressure and particle motion can alter how quickly processes happen or how matter behaves. Food storage, refrigeration, cooking and weather all give everyday ways to test the same particle ideas without needing specialist equipment.

Waves transfer energy and information without transferring matter from source to receiver overall. Frequency tells us how many oscillations pass each second, wavelength is the spacing between matching points, and wave speed links them through v = fλ. Different frequencies interact with materials differently, which is why engineers can choose particular parts of the electromagnetic spectrum—or particular sound frequencies—for sensing, communication, heating or imaging.