How is electromagnetic energy fromthe microwave transformed into heat energy

When light hits a white surface, rays are reflected. When light hits a black surface the light is changed to heat.

Infrared is electromagnetic energy. When it hits a material it causes the molecules to move faster which is showing more energy

Microwave energy is used to make food molecules hotter in the way explained above.

First, the microwaves transmit kinetic energy to the water molecules of the food, heating the water molecules. Only, those that are not very deep into the food.

Second, the hot water molecules transmit heat by conduction to the other parts of the food.

Explanation:

1) Microwaves are a form of electromagnetic radiation. The same as any wave, they carry energy.

2) The wave length of microwaves are in the range of 0.001 mm to 1 m (shorter than radio waves and longer than infrared)

3) The microwaves of an oven, used to heat food, have a wave length aroun 12 cm.

4) The microwaves transmit energy to the water molecules in the food, by increasing the kinetic energy of water molecules. As result, the water molecules get hotter. Microwaves only penetrate about 1 cm inside the food (a potato for example) and from that the heat is transferred by conduction to the inner parts of the food.