2. F ˆ F www.schoolDD.com 1
12
12.1
- F
( F F F F F F F
)
- F F F F F
F F F F F
F F F F F F
F ˈ F F ˆ
ˈ
1. F
2. F
F ( )
F
F F ( ) F
A1A1 N2N2
A2
A2
N3 N3
A3
A3
s2s1
N1
A0 N1
F F F
F A
C > B > A
A B C
F
F
3. F ˆ F www.schoolDD.com 2
3. F F
4. F
12.2
- F F F F
- F ( T v λ
F f )
- ( vt ) t
F F F F
F F ˁ F F F
F F F
F F
˂ F F F ˂ F
F F F
F F F
F F ˂ F
vt = 331 + 0.6t -50° C ≤ t ≤ 80° C
F F F F F F F
F ˆ F F
F
v
vt
4. F ˆ F www.schoolDD.com 3
ˈ F (v) F
v = (m/s)
f = ( / Hz)
λ = (m)
12.3 F
ˈ F
F
. F F F
. F F F
ˈ F F
v = f ૃ
F
F
F
5. F ˆ F www.schoolDD.com 4
. ˈ F F F
F F F F F ˈ F
. ˈ F F
F F
F
- f F ˈ F
F 1
F F F F F
F F F 2 F F F ˈ F
F 1500 m/s
F 2
F 25˚ C ˈ 35˚ C ˈ F
F vt = 331 + 0.6t
t = 25˚ C , v25 = 331 + 0.6(25) = 331 + 15 = 346 m/s
t = 35˚ C , v35 = 331 + 0.6(35) = 331 + 21 = 352 m/s
= 352-346 = 6 m/s Ans
s = vt
= 1500 (2/2)
= 1500
s = 1500 m Ans
v = 1500
t = 2
s
6. F ˆ F www.schoolDD.com 5
F 3
F F F F F
F F F 6.0 cm F F F F
340 m/s
F F F F
F F 6.0 cm
v = fλ
f =
୴
=
ଷସ
.
= 5.67x103
Hz Ans
F 4
ˀ F F F F F 2 ˀ ˈ 2 4
F F 340 m/s
s1 s2 s = vt
s1 = vt1 = 340(2/2) = 340 m
s2 = vt2 = 340(4/2) = 680 m
F F s = s1 + s2 = 340 + 680 = 1020 m Ans
12.4 F F
F I F F F F
F ˈ F F (W/m2
)
P F I ן
ଵ
ୖమ
P = (Watt)
R = F F s
F F
I =
۾
ૈ܀s
R
t2 = 4t1 = 2
s1 s2
ˆ
7. F ˆ F www.schoolDD.com 6
F ࢼ ˈ F F ˈ (dB)
- F F F ˆ F
- F F
- F ( Tr ) F 60 dB
F 5
22 F F F ˈ F
F 140 F
F I =
ସୖమ =
ଶଶ
ସሺ
మమ
ళ
ሻଵସమ
ࢼ = 10 log ሺ
۷
۷
ሻ
I = F F
I0 = 10-12
W/m2
F F
F F
Imax = 1 W/m2
F
F ˆ F
ߚ
f
F
Tr
60 dB
0
ߚ
t
s
R = 140
s P = 22
8. F ˆ F www.schoolDD.com 7
I = 1x10-4
W/m2
Ans
F ߚ = 10 log ሺ
୍
୍బ
ሻ
= 10 log ሺ
ଵషర
ଵషభమ
ሻ
ߚ = 80 dB Ans
F 6
F A B F F ˈ 50 100 F A F
F 4x10-2
W/m2
B F F F
F I =
ସୖమ
P I ן
ଵ
ୖమ
୍ఽ
୍ా
=
ୖా
మ
ୖఽ
మ
IB = IA ሺ
RA
2
RB
2ሻ = 4x10-2
ሺ
502
1002ሻ
IB = 1x10-2
W/m2
Ans
F 7
F F ˆ F ˈ F F F ˆ
F F 1 W/m2
F ߚ = 10 log ሺ
୍
୍బ
ሻ
= 10 log ሺ
ଵ
ଵషభమ
ሻ = 10 log 1012
= 10 x 12
ߚ = 120 dB Ans
F
RB = 100
P
RA = 50
A
B
IA = 4x10-2
IB = ?
9. F ˆ F www.schoolDD.com 8
12.5
F (f ) F
F F F F 20 20,000
Hz F 20 Hz F F F 20,000 Hz F
F F F
20,000 Hz20
F F
ˈ
F
10. F ˆ F www.schoolDD.com 9
- F ˈ 2 F F F
C 256 Hz F C 256x2 = 512 Hz ˈ F
F F , F F
f , 2f , 3f , , nf ( F ) F F F F
F F F F F
ˈ F F F F
F F F 1
F F F ˈ F
F F 2 F 3 ˈ 2 3 F
( f , 2f , 3f , , nf )
- F F F F f , I n F
F 8
F 350 Hz F 1, 2, 3 4
F 1 , f = = 350 Hz
F 2 , 2f = 2(350) = 700 Hz
F F nf , In
3f , I3
2f , I2
f , I1
nf , In
3f , I3
2f , I2
f , I1
F
nf , In
3f , I3
2f , I2
f , I1
ʾF
11. F ˆ F www.schoolDD.com 10
F 3 , 3f = 3(350) = 1050 Hz
F 4 , = = Hz
12.6 F
F F
- F
- F F
F ˈ F F F F
F F F
F
F F F
F F F F F
F
λ/4 λ/2
12. F ˆ F www.schoolDD.com 11
F 9
F F F 680 Hz F
ˈ 340 m/s F 1 , 2, 3 F ˈ
F
F f = 680 Hz v = 340 m/s
λ =
୴
=
ଷସ
଼
= 0.5 m
F 10
F F F F ʽ F
1.0 m F 340 m/s
F F
F F
ସ
= F
λ = 4x1 = 4 m
f F f =
୴
=
ଷସ
ସ
= 85 Hz Ans
F 11
F F ʽ F F F F F
F F F F F 2 F F F
F 10 cm 2 F 20 cm F F
ˈ 340 m/s
s1 =
ସ
=
.ହ
ସ
= 0.125 m Ans
s2 = ?
s1 = ?
F
F
λ/4 λ/2
F
s2 =
ସ
+
ଶ
=
ଷ
ସ
=
ଷ୶.ହ
ସ
= 0.375 m Ans
λ/4
13. F ˆ F www.schoolDD.com 12
ଷ
ସ
-
ସ
= 0.20 0.10 = 0.10
λ = 2x0.1 = 0.2 m
f F f =
୴
=
ଷସ
.ଶ
= 1700 Hz Ans
12.7 F
F ˈ F F F F F
F F F ˈ
F F F F
F 12
F F 2 F F F 514 Hz 510
Hz
F Δf = | f2 f1 |
= | 510 514 |
Δf = 4 Hz Ans
Δf = | f2 f1 |
f1 = F 1
f2 = F 2
∆f ≤ 7 F F
0.10
3λ
4
0.20
λ
4
14. F ˆ F www.schoolDD.com 13
12.8 F F
ˈ F F ˆ (Observer) F F
(Source) F F ˆ
s
1. F F ˆ
F ˆ F F F
ߣ =
୴
F ߣO =
୴ି୴౩
౩
fO = ୴
ో
= ሺ
୴
୴ି୴౩
ሻfs
F ˆ F F
ߣ =
୴
F ߣO =
୴ା୴౩
౩
fO = ୴
ో
= ሺ
୴
୴ା୴౩
ሻfs
F F ˆ
F
vs t
vtvt v =
vs = F
vO = F ˆ
fs = F
fO = F ˆ F
ߣO = F ˆ F
15. F ˆ F www.schoolDD.com 14
2. F ˆ F F
F ˆ F F F F
f =
୴
ఒ
F fO =
୴ା୴ో
ఒ
ߣ =
୴
౩
fO = ሺ
୴ା୴ో
୴
ሻfs
F ˆ F F F
f =
୴
ఒ
F fO =
୴ି୴ో
ఒ
ߣ =
୴
౩
fO = ሺ
୴ି୴ో
୴
ሻfs
F F
F ˆ F
F F
1. F F F ˆ ( vO = 0 ) F fO = ሺ
୴
୴േ୴౩
ሻfs
- F F ˆ F F F fO F fO = ሺ
୴
୴ି୴౩
ሻfs
- F F ˆ F F fO F fO = ሺ
୴
୴ା୴౩
ሻfs
- ߣO F ߣO =
୴
ో
vO vO
v
s F
fO = ሺ
ܞേܞܗ
ܞേܞܛ
ሻfs
16. F ˆ F www.schoolDD.com 15
2. F F ˆ F F ( vs = 0 ) F fO = ሺ
୴േ୴ో
ሻfs
- F F ˆ F F fO F fO = ሺ
୴ା୴ో
ሻfs
- F F ˆ F fO F fO = ሺ
୴ି୴ో
ሻfs
- ߣ F ߣ =
୴
౩
3. F F F ˆ F F F 1 2
F 13
ʽ 1000 Hz F ˈ 340 m/s
F ˆ F
. F 40 m/s F F ˆ F F F
. F 40 m/s F ˆ F F
. F ˆ F 10 m/s F
. F ˆ F 10 m/s
F
F ˆ F fO = ሺ
୴േ୴
୴േ୴౩
ሻfs
. vs = 40 m/s F , vO = 0
fO = ሺ
୴
୴ି୴౩
ሻfs
= ሺ
ଷସ
ଷସିସ
ሻ1000 = ሺ
ଷସ
ଷ
ሻ1000
fO = 1133 Hz Ans
. vs = 40 m/s , vO = 0
fO = ሺ
୴
୴ା୴౩
ሻfs
= ሺ
ଷସ
ଷସାସ
ሻ1000 = ሺ
ଷସ
ଷ଼
ሻ1000
fO = 895 Hz Ans
vs
vO
vO
fs = 1000
v = 340
F
17. F ˆ F www.schoolDD.com 16
. vO = 10 m/s F , vs = 0
fO = ሺ
୴ା୴
ሻfs
= ሺ
ଷସାଵ
ଷସ
ሻ1000 = ሺ
ଷହ
ଷସ
ሻ1000
fO = 1029 Hz Ans
. vO = 10 m/s , vs = 0
fO = ሺ
୴ି୴
ሻfs
= ሺ
ଷସିଵ
ଷସ
ሻ1000 = ሺ
ଷଷ
ଷସ
ሻ1000
fO = 970 Hz Ans
12.9
F F F
F ˈ
F F F
F F F F F
F F F F F
F
s
F
