Phys 375 – Prof. Hall
Homework #6, due November 10&11, 2008
1) (5 points) Pedrotti, problem 11-1.
2) (5 points) Pedrotti, problem 11-3.
3) (5 points) Pedrotti, problem 11-4.
4) (9 points) In class we saw that the electric field amplitude for a double slit diffraction
pattern is given by
⎥
⎦
⎤
⎢
⎣
⎡+= ∫∫ +
−
−−
+−
−2/)(
2/)(
sin
2/)(
2/)(
sin
)(
0
0ba
ba
iks
ba
ba
iks
tkri
L
Pdsedsee
r
E
E
θθ
ω
where a is the slit spacing and b is the slit width. Evaluate the integrals and show that
α
β
β
ω
cos
sin2 )(
0
0tkri
L
Pe
r
bE
E−
=
where
θβθα
sin
2
1
,sin
2
1kbka == .
5) (9 points) Sketch the diffraction patterns that you would observe on a screen 100 cm
from an aperture illuminated by a He-Ne laser, for the following cases:
a) single slit, slit width = 20 microns.
b) double slit, slit width = 20 microns, slit spacing = 80 microns.
c) four slits, slit width = 20 microns, slit spacing = 80 microns.
Draw these diffraction patterns on a one-to-one scale as you would see them on the
screen, and label the position of the first zero due to the "slit width" term.