Jim Guinn’s PHYS2212 Assignment #24 Solutions
1.
Consider a ray that is entering and reflecting off of a series of thin layers as shown.
For each of the reflections at
“a” through “e”, will there be a
180
o
phase shift or not?
a.)
Yes, since 1.36 > 1.00 .
b.)
Yes, since 1.46 > 1.36 .
c.)
No, since 1.33 < 1.46 .
d.)
Yes, since 1.50 > 1.33 .
e.)
Yes, since 1.52 > 1.50 .
2. A laser with a wavelength of 635nm shines on a single slit with a width of 4.25x10
5
m. A
flat screen is located 3.00m from the slit. How wide (in meters) is the central bright fringe?
That is, how far apart are the two dark fringes bordering the central bright fringe?
The angle from the center of the central bright fringe to its edge, i.e. to the first dark
fringe (m = 1) is given by
sin
θ
= m
λ
/ W = 1 x 635x10
9
m / 4.25x10
5
m = 0.0149 , so
θ
= 0.856
o
.
The distance from the central axis to this fringe is
3.00m tan(0.856
o
) = 4.48x10
2
m .
n = 1.50
n = 1.36
n = 1.00
n = 1.46
n = 1.33
n = 1.52
a
b
c
d
e
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The width of the fringe is twice this distance, so
width = 2 x 4.48x10
2
m =
width = 8.97x10
2
m .
3. In the singleslit experiment described above, how wide is the second bright fringe (in
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 Spring '11
 JimGuinn
 Frequency, Wavelength, θ, central bright fringe

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