I once read that it is not the velocity of particles that determines temperature, but the width of the velocity distribution. Thus a bunch of atoms all moving as a cluster in perfect sync would have a temperature of 0K. I suspect this is how they use lasers to create Bose-Einstein condensates...
We're told that all electromagnetic radiation consists of photons. But you never hear them mentioned when discussing low-frequency radio waves. Why not? I get that, due to the low frequencies, the energy of each individual photon would be very small, so there must be lots and lots of them flying...
Exactly. Which is why two different color samples can appear identical to the eye under, say, incandescent light, but look quite different when taken outside in the daylight. The different spectra of the illumination cause the proportions of reflected wavelengths to be different. What we call...
Most of the answers here seem pretty technical to me. Let me try a simpler version:
I like to think of a class as a pad of blank forms, like those pink pads that used to be common for taking phone messages. The form has spaces to write in information like Caller's Name, Phone Number, Message...