In USMA 26319 I mentioned 30� and 60� (30 degrees and 60
degrees).That is what I wrote, and it was echoed back to me
correctly. In USMA 26334 and 26335 it was quoted as 300 and 600.
Evidently there was some incompatible software involved.
I may have left the impresssion that I am anti-radian. I am in favor
of the radian in its place. Torque is usually said to be newton
metre. I think it would more accurate to say that it is joule per
radian and that it is a vector quantity.
Angular velocity may be described as radian per second and angulqar
acceleration may be described as radian per second squared.
The steradian is involved in the definitons of radiant intensity and radiance:
radiant intensity is watt per steradian;
radiance is watt per square metre steradian;
and in the definitions of photometric units:
luminous flux or lumen is candela per steradian,
luminance is candela per square metre,
iluminance or lux is lumen per square metre.
Note that radiant intensity is watt per steradian while lumen is
candela per steradian; and radiance is watt per squae metre steradian
and lux is candela per square metre steradian. There is no special
name for watt per square metre which corresponds to candela per
square metre or luminance.
The candela is defined in terms of the sensitivity of the normal
human eye. "The candela is the luminous intensity in a given
direction of a source that emits monochromatic radiatioon of
frequency 540 x 10^12 hertz and that has a radiant intensity in that
direction of 1/683 watt per steradian".
--
Joseph B. Reid
17 Glebe Road West
Toronto M5P 1C8 Telephone 416-486-6071
