Remote Medicine

I missed posting last week, since we were busy driving to our new home of Gainesville, FL! I have a new postdoc with the university, which I'll talk about in a later post. This week though I wanted something a bit shorter, since we've got several rental viewings to go to. I thought I'd try to expand on something I wrote on Facebook a few months ago, at the start of the lockdowns.

My friend Seth wrote that he didn't have a thermometer on hand, and most stores were sold out. I offered this suggestion:

Here's an idea I just had that could work in theory: If you have a TV remote and a voltmeter, you could press the remote against your head, and measure the voltage across the LED, which will be proportional to the infrared light emitted by your skin, which in turn is proportional to your temperature. Physicist Survival Skills!

I've mentioned TV remotes before, but this idea doesn't use the IR LED in the typical way. While LEDs are designed to emit light (as the name implies), they can also generate voltage when they absorb light near their own wavelength. You can see a demonstration of both uses in this video:

The question is how to calibrate the "thermometer" so we can convert between voltage and temperature. We need some known temperatures we can sample. Two possibilities I thought of were boiling water, and (assuming you haven't fully switched to fluorescents) incandescent light bulbs. Depending on your elevation, water will boil around 373.15 Kelvin, and bulbs emit light according to the blackbody distribution at 2400 K. That means your temperature (in Kelvin) will be

As usual though, ramblings from a crazy physicist are no substitute for healthcare, so I do not endorse the use of improvised TV thermometers. Thanks for a great idea, Seth, and stay healthy everyone!