光波爐的原理是甚麽?

You probaly have been misled by the term "light"(光). In Chinese, the term 光 not only covered visible light, but electromagentic waves of other ranges. For example, X-rays(X-光), ultraviolet(紫外光). These are invisible "lights", but still named as 光 in Chinese.

光波爐 is, in fact, Halogen Cooker. It uses strong infrafred (commonly known as "hot light"(熱光) ) to cook the food. An halogen bulb contains the halogen gas, either bromine or iodine, under pressure such that its temperature, when in operation, is much much higher than conventional light bulb. This serves as a heat source for cooking.

You may refer to the following web-page for detailed explanation of Halgen Cooking Pot.

http://www.explainthatstuff.com/halogenhobs.html