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Measurement units of light



John Roeder asks.........

What is the relationship between the cd and W/m^2 lighting ?
The difference seems to me to be that that
the cd refers to energy intensity at a given wavelength and that this is
of
significance because the eye is not equally sensitive to all frequencies,

just as the varying sensitivity of the ear to different frequencies
necessitates different frequency weightings for different decibel scales.
Is
the distinction between cd and W/m^2 too subtle for ninth
graders.

John Roeder jlroeder@aol.com