'07'08
Ph213  Exam 1
Name:
Slot:
" Since you don't have calculators, answers may be left
in
'unevaluated form' such as x
=
(3+sin(n/3)!(13)1/2.
" The speed
of
sound
in
air
is
330
m/s.
•
Unless told otherwise, assume
that
the amplitude
of
sound waves does
not
decrease
with
distance.
•
Do
all
work on
the
attached sheets.
Blue
books are for scrap only!
1.
A Ph213 student
is
walking parallel to a tall construction fence
that
has
three narrow vertical openings (slits)
of
equal
width
whose centers are 0.4 meters apart.
Far
away construction is producing
an
irritating 10
khl
pure tone. Anxious
to
test her knowledge
of
interlerence, the student pulls
out
her Radio
Shack
sound intensity
meter
and measures
an
intensity
of
1
0
directly across from the opening,
20
meters from
the
fence.
Moving 1.0 meters parallel to the fence, she
finds a
drop
in intensity
to
C1
0
.
(You may want
to
treat
20
meters
as
much
farger
than 1 meter.]
a.
Sketch the phasor diagram
that
could be used
to
determine
the
constant
C.
Since you
don't
have a
protractor
or
calculator, I can't expect you
to
draw
the phasors at the actual angles,
but
write
an
expression
for
the angles between
the
phasors and
try
to
make a generally correct sketch that includes the labeled angles.
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 Spring '08
 Faculty
 Phasor Diagram, KHL, Shack sound intensity

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