Physical Optics
Class: Physics 182 Lab Summer II
TA: Joy Ding
Date of Experiment: 7/27/10
Due Date: 7/30/10
Itzel Rodriguez
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Goal of experiment:
The purpose of this lab was to work with and understand Huygens’ Principle and
the Superposition Principle. Understanding these two methods would help explain diffraction patterns in
diffracted light for example single, double, and multipleslit diffraction.
Introduction:
This lab dealt with breaking down the assumptions previously made in geometrical optics.
Physical optics studies cases when the size of the light itself is very similar to the size of the optical
device. The reason why lights diffraction goes around a corner is because of its wavelike nature. When a
small wavelet adds to every other wavelet it is known as the Principle of Superposition as seen in Picture
1.
Its important to know that because it will help better understand Huygens Principle which states that
Every single spot of a wave front could be deemed the basis of secondary wavelets that expand out in all
directions with the same speed as that of propagation of the waves as seen in Picture 2. With the help of
mathematical deftness one can calculate what occurs when the wavelets created hamper with parts of the
screen. At points O and P where they are opposite to the middle of the slit, wavelets add up together due
to the fact that they travel the same distance L
b
. h is the distance away from the midline or better known
as the central maximum which shows
how the wavelets start to cancel because they travelled in different
directions and the total calculation happens when
≃
/
h
Dλ a
where
a
the width of the slit, D is the distance
between the slit and the screen, and l is the wavelength and that is just an estimate of the more general
equation
=
asinθn
nλ
. In order to predict the size of the central maximum the following equation will be
needed
=
ahnD
nλ
and then multiplied by two to get the full size. Now it’s time to talk about the
maxima using two or more slits. The maxima unlike the first part are the position of the open spots and
not the dark spots. In order to find the maxima the following equation will be needed
=
λ
dsinθm
. As
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 Summer '08
 greg
 Work, Diffraction, central maximum

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