Asked by: Anonymous
Temperature is a measure of the average speed of the molecules in a substance. When you heat something in a microwave oven, the electromagnetic radiation stimulates the molecules to move faster and the food gets hotter. This is similar to the way that you feel warm in the sun, except that microwaves have a longer wavelength than visible light, so they penetrate further into the food.
If you put food in the fridge, collisions with the surface molecules and the slower, colder air molecules will transfer energy away. A hot cup of tea also loses energy as the fastest molecules break free of the liquid and become vapour, reducing the average speed of the ones that remain.
This is called evaporation.
The third way for something to lose heat is by radiation. Just as adding electromagnetic radiation to a body will cause it to become hotter, so hot objects will emit electromagnetic radiation (mostly as infrared) as they cool. In a sense, this is a ‘reverse microwave’, but the problem is that you can’t ‘suck’ radiation out of something any faster than normal. The rate at which a body radiates energy depends on what it’s made of, its surface area and how hot it is. There is no magic ray you can add that will influence this.