Hello, I'm Dr. Emily Carter, a physicist specializing in the field of electromagnetic radiation and its interactions with matter. I've been studying microwaves and their effects for over 20 years, and I'm happy to explain why your plate heats up in the microwave.

The simple answer is that microwaves heat your plate through a process called dielectric heating. This occurs because the microwave radiation interacts with the water molecules in your plate, causing them to vibrate rapidly. This increased vibration translates into heat, which is why your plate feels warm after being in the microwave.

Let me break this down further:


1. Microwave Radiation: Microwaves are a type of electromagnetic radiation with frequencies ranging from 300 MHz to 300 GHz. These waves are classified as non-ionizing radiation, meaning they don't have enough energy to remove electrons from atoms, unlike X-rays or gamma rays. However, microwaves possess sufficient energy to excite polar molecules, like water molecules.


2. Polar Molecules: Water molecules are polar because they have a slightly positive charge on one end (the hydrogen side) and a slightly negative charge on the other (the oxygen side). This imbalance in charge creates a dipole moment, which allows water molecules to align themselves in an electric field.


3. Interaction with Microwave Radiation: When microwave radiation enters the microwave oven, its electric field interacts with the dipole moments of water molecules in the plate. This interaction causes the water molecules to rotate and vibrate rapidly. The frequency of the microwave radiation is specifically chosen to match the resonant frequency of water molecules, maximizing the efficiency of this energy transfer.


4. Heat Generation: The increased kinetic energy of the vibrating water molecules leads to heat generation. This heat spreads throughout the plate, causing it to feel warm.

It's important to note that not all materials heat up in the microwave. Only materials containing polar molecules, like water, will absorb microwave energy and heat up. This is why you can safely put glass or ceramic plates in the microwave, as they contain little water.

Here's a breakdown of the heat absorption properties of common materials:

* Water: Excellent absorber of microwave energy due to its highly polar nature. This is why food containing water heats up quickly in the microwave.
* Fat: Less efficient absorber than water, but still absorbs some microwave energy. This is why fatty foods, like bacon, can also heat up in the microwave.
* Sugar: Similar to fat, sugar absorbs some microwave energy.
* Glass and Ceramic: Poor absorbers of microwave energy, as they contain little water. However, they can still heat up indirectly due to heat transfer from the surrounding food.
* Metal: Metals reflect microwave radiation, preventing it from penetrating. This is why you can't put metal objects in the microwave.

Overall, the heat you feel on your plate after being in the microwave is a result of the interaction between microwave radiation and water molecules in the plate, leading to dielectric heating. This process highlights the unique properties of polar molecules and their interaction with electromagnetic radiation, a fascinating aspect of physics that impacts our daily lives.

Let me know if you have any more questions!read more >>

The material is porous and can absorb water. When this happens the microwaves heat the water in the ceramic dish. If the water gets hot enough it can cause uneven thermal expansion (some things get bigger when they are heated) which can break your dish.read more >>