COMMENTS ON NiNTH PROBLEM SET - SPRING 2003

	These are fairly straightforward, and may be done fairly
	easily if the text (B&B) is consulted.  "Index" is not in the
	index, but don't let that stop you.

	9.1(a):  A full appreciation of this problem would involve
          some knowledge of the physiology of the eye, but this won't
          affect the answers.

	9.1(c):  The text quotes the result on Page 483, making
          reference to "performing a few simple trigonometric
          manipulations."  Performing these relations is now up to
          you.

	9.1(d):  If you know where to look in B&B, this is done for
          you, more or less.

	9.2:  Many hints for this were contained in the lecture of
          April 30.  The first part of the problem is more or less a
          yes/no question, but of course you can and should justify
          any answer you give.

	9.3:  Again, similar to what was done in lecture.  Consider
          what assumptions goe into your "estimate".

	9.4:  You're not asked specifically, but when you get an
          answer for N_(min), making a plot of the intensity as a
          function of angle psi helps a great deal in aiding
          understanding.  For part (c), I'm told that this method of
          tracking incoming aircraft is fairly new, as in the past few
          years.