This preview shows pages 1–4. Sign up to view the full content.
1
1070 Practice Final Exam Solutions – W’08
1.
Travelling sound wave in +x direction
Forms for travelling wave are:
y= y
0
sin (2π
−
)
= y
0
sin [ω(t −
)],
ω = 2π
f
=
∴
Can only be (C) or (D)
Angular frequency ω= 2πf,
f
=
∴
f
=
= 2000 Hz
∴
ω = 4000 π
=
=
where
v
= 340
∴
y = y
0
sin [4000 π (t 
) ]
ANS (C)
2.
“Intensity level”,
IL at 15m
0
IL = 10
og
I
I
Given as 85 db
∴
0
I
I
= ℓog
1
(8.5)
∴
I
=
I
0
(10
8.5
)
The s
tandard reference intensity
I
0
= 10
12
w/m
2
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document 2
∴
I
= 10
12
10
8.5
= 10
3.5
= 10
+0.5
10
4
=
x 10
4
= 3.16 x 10
4
w/m
2
“Power” =
IA
where (
A
=area)
A
= 2.0
1.0 m
2
= 2.0 m
2
∴
P
= (3.16
10
4
)
2.0 = 6.32
10
4
w
ANS (A)
(note, the distance
15.0 m is irrelevant
)
3.
“Beat Frequencies”
If two waves of frequency f
1
and f
2
are added, the beat frequency f
B
is
f
B
=  f
1
– f
2

(Abs. value is not in text, but
is
in lab manual)
∴
5 =  f
string
 440 =  f
string
– 450 
The only common solution is f
string
= 445, hence the 2
nd
harmonic is at
2(445) = 890 Hz,
ANS (B)
4.
Clearly, only (D) is false
5.
Lens
r
1
r
2
oil (
n
2
)
light
water (
n
1
)
By conventions, both
r
1
and
r
2
are positive.
3
The “Lensmaker Equation” is
P = (
) – (
) = (
) – (
)
=
+
= 2.9
ANS (E)
6.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview. Sign up
to
access the rest of the document.
This note was uploaded on 12/08/2011 for the course PHYS 1070 taught by Professor Forgot during the Fall '09 term at University of Guelph.
 Fall '09
 Forgot

Click to edit the document details