Microwave Math That Einstein Would Have Loved

Measuring the speed of light with a microwave is a pretty standard DIY experiment, though I prefer using chocolate chips, given the premise that one should eat the experiment if it’s about food. (Then again, the article suggests Velveeta. Put that on your spam and wonderbread sandwich and it’s still food-free). Sure, Einstein might have liked that.

My nit is with this

To get the most out of your microwave, it helps to understand that it cooks with light waves, much like a grill does, except that the light waves are almost five inches (12.2 centimeters) from peak to peak—a good bit longer in wavelength than the infrared rays that coals put out.

A grill is not really that much like a microwave. A microwave uses (non-thermal) radiation to cook food. A grill uses convection, conduction and radiation. If it just used radiation, you could put a transparent* vacuum system in between the food and the coals and still cook the food, but that wouldn’t give you the expected result. The air is hot, as is the grill itself — you get a pattern burned into your hamburger patty or hot dog from where it lies on the hot grill. Conduction and convection. All three modes of heat transfer play a role.

What is said about the wavelength isn’t wrong, but it does tend to reinforce the mistaken conception that infrared radiation is synonymous with heat. The blackbody radiation that would be emitted wouldn’t have a specific wavelength, since it would be a continuum, and it would include wavelengths longer and possibly shorter than IR, if the source were hot enough. The microwaves, of course, are not heat in a physic sense — in thermodynamic terms that would be considered work, since they do not come from a thermal source; it’s not coming from a temperature difference. An infrared laser could be used to cook, but that wouldn’t be heat either.

I really have no idea if Albert would have liked or disliked such an example, but I suspect glossing over details that give the wrong implication might have bothered him.

*Certainly not one made of pyrex