Does Microwave Radiation Remain On Plates Or Bowls When They Come Out Of The Microwave From Cooking?

Microwaves are electromagnetic radiation of insufficient energy to cause ionisation. Ionisation involves physical change of the structure of elements. Gamma radiation or X-rays are ionising radiation, where the very nature of chemical elements can be changed, and in this case they may become radio-active in some cases, so be able to influence other objects in a related way. This seems to be what you are thinking about. Nevertheless ionising gamma irradiation of food has been used to kill bacteria etc, and any changes do not appear to be significant. It is to do with the energy levels of the radiation, which are related to wavelength of the electromagnetic radiation. Radio-active describes something that "gives off a ray" but it also means the ray is an ionising one. There is no change to radio-activity at all associated with microwave, infra-red or light waves. The concrete walls or a granite hill may have its own natural radio-activity, part of the background radiation we live with.

With microwave radiation there is no such ionising behaviour. The heating is a form of dielectric heating. Only some materials absorb microwave radiation. Water is the most likely, so food through the water in it. Glass, plates and many other materials may or may not even be heated. They are often transparent or reflective. The elements in the materials do not become ionised by microwave ovens. That is why it is called non-ionising radiation. The wavelength of microwaves used for cooking is of the order of 122mm and light waves (green) are of the order of 1/4 million times shorter, yet light waves still do not ionise materials. Gamma radiation is a much shorter wavelength than light.

Microwaves are a type of radio wave, and behave like light or heat (infrared). Think of the sun. Most of the energy from the sun is visible light. The light shining on your skin makes it feel warm as the energy is absorbed, but there are no changes to chemical elements involved. The skin does not become radioactive or give off light of its own after you go inside. Certainly leaving your CDs in the sun would not help because they get hot, and also some photo degradation of chemicals like plastic and dyes used in paint or printing can occur over a long period of time. There are chemical reactions that involve light (which has higher energy than microwaves anyway). These chemical reactions are not to do with ionisation. For example plastic can deteriorate, and your skin gets darker or a photograph can be captured on a film. Sunburn is caused by the small amount of ultraviolet rays present in the sunlight, which are getting closer to the ionising energy levels. In fact ionising radiation is considered to start in a minor way around far UV, wavelength 121nm. That is one million times shorter in wavelength than the microwave oven, so a dramatically different form of electromagnetic radiation.

As you said, putting your CDs in the microwave oven is not a good idea, any more than putting them in a conventional oven, which uses infrared (heat) radiation instead of microwave radiation mostly.

Once the food and plates etc are taken out of the oven they do not radiate microwaves and certainly have not become ionised in any way. They do radiate heat waves caused by the microwaves being absorbed and converted to heat in the food. You can feel that heat radiation on your skin so you know what it means. It is no different to heating the food on a cooker or hot plate in a saucepan.

So your CDs and DVDs are safe from a plate of food that has been heated by the microwave oven as they would be from a plate of food heated in a gas or electric oven. Of course, if you put a hot plate of food on a CD, it will likely be damaged by the heat.

What is ionisation in this context? What you are thinking of is caused by nuclear radiation (radio-active). Particles might be added or removed from atoms. When irradiated by "ionising radiation" the properties of an element can change. Thus it may behave chemically like another element. Strontium 90 was a product of atomic bombs that behaves like calcium chemically yet is radioactive. It can taken up by the body and incorporated in bones etc. but continues to ionise other elements in the body. Eventually this could cause cancers due to the damage in biological cells. Generally biological systems and electronic devices are the most sensitive, but very fierce ionising radiation is likely to affect almost any material. So does fierce heat, fierce mechanical blows, etc.

No. The "radiation" is electromagnetic radiation, so is light, infrared, ultraviolet and radio waves. It is not ionising radiation, which is associated with nuclear radioactivity. There is no danger from your plates, CDs etc., except that they may get hot from the hot food inside, just as in a "conventional" oven.