September 13, 2013
Here are a few other things that I wanted to say about microwave ovens and our vision. First, there’s a window in the door so you can see your food cooking. I don’t know that I’ve ever seen a microwave oven without a window. Yesterday I wrote a post about the frequency of the energy that microwave ovens generate (actually 2.45 GHz) but I didn’t say how long the wavelengths are. They are about 4.6 inches. There’s a simple formula to calculate that. I’ll be honest, this next part kinda makes sense but then I can’t fully explain this. Yet.
That screen in the microwave oven door has little holes so we can see through it. The spacing of those holes is about 1 mm. Or in inches, 0.039. Because the wavelength of the microwaves is so much larger than the hole size in the screen, the microwaves can’t get through. But visible light can get through because the wavelength of light is way smaller than those little holes. So in essence, that screen is like a solid wall for microwaves but not for visible light.
This next thing about that screen is something I can’t fully explain either but I think I have an idea why this thing I do works. If I don’t move my head when I’m looking through that screen I don’t see what’s inside very well. But if I move my head back and forth (side to side) in front of the screen I can see what’s inside much better. I looked up persistence of vision in wikipedia and of course, there was nothing about me moving my head side-to-side and cooking my food. But, the reason I can see better in the microwave when moving my head is that the images are quickly changing. I’m making a movie (sorta in reverse) by moving my head! I made that up but I think I’m pretty close to getting this right.
Movies are just a bunch of pictures that when shown at a certain rate it makes you think something is moving. A typical “frame rate” is 24 pictures per second. There is a fraction of time when there is nothing but we don’t see that. We don’t see that “black” moment. If you move your head in front of that microwave screen I’m guessing that those little holes are so small that you’re moving faster than 24 holes per second or enough to be obviously better than 1 hole per second. Because our visual system has a persistence that lasts the teeniest bit longer than when the actual image was there, it’s able to combine all those images into a clearer picture. Don’t hold me to this explanation too much but I’m onto something….I think. Someone else told me this is saccadic masking.
Try it anyway. Just move your head from side-to-side in front of the microwave while telling your family you’re not crazy.