Solutions to WebAssign HW #4  Giancoli Ch. 343, 8, 15, 16, 20, 29, 35, 36, 42; (due
2/18)
3.
For constructive interference, the path difference is a multiple of the wavelength, as given by
Eq. 342a. Apply this to the third order.
( )
9
6
3610 10 m
sin
3.9 10 m
sin
sin28
m
dmd
λ
θλ
θ
−
−
×
=→
==
=
×
°
8.
For constructive interference, the path difference is a multiple of the wavelength, as given by
Eq. 342a.
The location on the screen is given by
tan ,
x
=
l
as seen in Fig. 347(c).
For
small angles, we have
sin
tan
.
x
≈≈
l
( )( )( )
9
4
3
680 10 m
3 2.6m
sin
1.4 10 m
38 10 m
xm
md
x
−
−
−
×
=→=→
=
×
×
l
l
15.
The presence of the water changes the wavelength according to Eq. 341, and so we must
change
to
.
n
n
=
For constructive interference, the path difference is a multiple of the
wavelength, as given by Eq. 342a.
The location on the screen is given by
tan ,
x
=
l
as
seen in Fig. 347(c).
For small angles, we have
sin
tan
.
x
≈
≈
l
Adjacent fringes will
have
1.
m
∆=
( )
()
1
12
9
3
21
5
1
sin
;
;
470 10 m
0.500m
1
2.94 10 m
1.33 6.00 10 m
n
nn
n
m
m
dm
d
m
x
x
x
dd
d
m
m
xx x
d
n
d
λλ
−
−
−
+
=
=
=
→
×
+
∆= − =
−
=
=
=
=
×
×
l
ll
l
l
l
16.
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 Spring '08
 LIN
 Quantum Physics, Diffraction, Light, Wavelength

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