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Re: Angle of deviation



A few days ago Blair Drader wrote:

I require some clarification on what the angle of deviation
is.&nbsp; In the physics text <EM>Fundamentals of Physics an
Introductory Course</EM>, it states that it is the angle between the
original path of the incident ray of light entering a prism, and the
path that the emerging light ray.&nbsp; As far as I can tell, there
are 2 angles here, one greater than&nbsp;90 degrees, and one less
than 90 degrees.&nbsp; Is the angle of deviation defined to be less
than 90 degrees?

The only two answers I've seen so far suggest that the angle of
deviation is acute, but this is simply not so in general; angles of
deviation can be anything from 0 to 180 degrees. (The text might
have been clearer if it had said that the angle of deviation is the
angle between the *directions* of the incident and emerging light
rays.)

For instance, the primary rainbow is created by light rays that are
refracted twice and internally reflected once giving overall angles
of deviation that range from 138 to 140 degrees. The secondary
rainbow is created by light rays that are refracted twice and
internally reflected twice giving overall angles of deviation that
range from 127 to 130 degrees. (The sum of the individual angles of
deviation for the four interactions ranges from 230 to 233 degrees.)

--
John Mallinckrodt mailto:ajm@csupomona.edu
Cal Poly Pomona http://www.csupomona.edu/~ajm

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.