ericmazur / PnPbook

Tracking of typos, errors, and improvements for "The Principles and Practice of Physics"
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some non-SI units #210

Open JohnDenker opened 7 years ago

JohnDenker commented 7 years ago

*) In the appendix on page A-4 it says the "SI unit" of optical strength is the "diopter".

I'm pretty sure the official SI unit is meter^-1, whereas diopter and dioptre are non-SI nicknames.

*) Similarly on page A-2, the "SI unit" for angle is given as degree, radian, and revolution.

For starters, cycle would be better than "revolution". A sound wave may have a frequency of 100 Hz, i.e. 100 cycles per second, even though it does not "revolve" at all.

Also, I don't recall any SI documents that tolerate "degrees" as a unit of angle.

We agree that SI is hopelessly confused about radians versus cycles.

*) On page A-3, it is inconsistent to say that phase is "unitless" when angles have units. See also item #50 (units versus dimensions). I think of phase as an angle, especially in the context of "simple harmonic motion" (as it says on page A-3).

For anharmonic motion things get weird, but that's beyond the scope of the book.