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PHYS1002
2007
Tutorial Sheet No 7
Due: Friday 14/09/07 (Q14) 5.00 pm
These tutorial sheets are intended to supplement your learning from lectures, they do this by
giving you problems that require you to apply the information that you cover in lectures.
Sometimes it is necessary for you to use other resources that are available to you to be able to
do the assigned problems, for example texts or your tutors. We feel that this is an important
part of the course  all students need to learn to work independently and from various
information sources. This is why we encourage you to regularly use the textbook, and also to
consider looking at other textbooks in order to get a thorough understanding of this subject.
Research is an essential skill that all students need to develop and we write tutorials that try to
aid this development.
So, when attempting the tute sheets each week be aware that you will probably need a number
of problemsolving strategies and that these may include referring to sources that are outside
your lecture notes. Also be aware that your lecturers, tutors and the Physics Learning Centre
are there to help you and to provide you with information that will help you with your
assignments.
Study Guide
Make sure you understand vergences. Using them is a clever way to calculate problems
in optics.
Tipler and other textbooks use a different approach. There are additional resources
on vergences available on the internet, go to the PHYS1002 web page and check out the link
to
http://www.physics.uq.edu.au/people/mcintyre/vergences
for a comprehensive introduction
to vergences, and plenty of interactive examples.
1.
Vergences are very useful analytical tools. Vergence quantifies the amount of curvature of
a propagating wavefront – this is analogous to the angular spread of a beam. By
convention, we denote converging beams with positive vergence and diverging beams
with a negative vergence. The word ‘vergence’ comes from (con/di)vergence.
2.
Why use vergences? They are an alternative to using ray optics solution techniques such
as the mirror and lensmaker equations. In fact, vergences are a more general and powerful
technique. Not only can you solve multiple element systems easily, but vergences are also
linear. This means that you can consider a multiple element system as one superelement
having a power equal to the sum of the powers of the individual elements.
3.
It is important to remember that at large distances away from a source, a wave can be
considered to be planar, and thus has a vergence of zero. There are some special cases,
such as lasers, which generate light that can be considered to be plane waves even at short
distances from the source.
4.
An object is generally seen by diverging rays scattered off it, so the vergence of this light
is negative.
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 Three '11
 TarasPlank
 Magnetism, refractive index, optical power

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