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Ultrasounds
Moduson table
Ref :
223 008
For the minima, we have δ=
Since
For a=4 cm, we have
Since -π/3
-0.866
The possible values of k for the amplitude minima are:
When
• we have for the peaks: θ≈sin(θ )=k.λ/a=0.21.k, with k=-2, k=-1, k=0. k=1 and k=2
• we have for the minima: θ≈sin(θ )=(2k+1).λ/2a=0.105.(2k+1), with k=-2, k=-1, k=0. k=1
Comparison of experimental and theoretical results
The experimental measurements obtained agree fairly well with the theoretical results.
ENGLISH
Number of minima
2 (
λ
is constant for a given value of a,
a 2
λ
, 0
=
a 2
≤
≤
θ
+π/3, we have -0.866
≤
+
≤
, 0
105
.(
2
k
) 1
+0.866 or encore -4.63
k=-4, k=-3, k=-2, k=-1, k=0. k=1, k=2, and k=3
Case of small angles
θ
is small (for θ = about 25 deg. about on both sides of position M
sin(
)
θ
=-24.2°: θ
-2
and k=2
θ
=-18.4°: θ
-2
•
As for the number of peaks and the number of minima, the extreme negative values
could not be obtained but the other 8 ones could be observed.
•
With small angles, the difference between the experimental positions and the
theoretical values is slight:
Experimental peak
(in degrees)
Theoretical peak
(in degrees)
Experimental minimum
(in degrees)
Theoretical minimum
(in degrees)
λ
θ
+
≈
k
). 1
a
sin(
)
sin(
or
2
θ
sin(
)
is a integral multiple impair of
84
=
, 0
105
sin(
and on a
8
θ
≤
≤
sin(
)
+0.866, or
≤ k
≤
=0° ; θ
=12.1° ; θ
=-12.1° ;θ
-1
0
1
=6° ; θ
=18.4° ; θ
=-6° ;θ
-1
0
1
-18
-6
-18.4
-6
-24
-12
-24.2
-12.1
50
λ
+
2 (
k
). 1
θ
≈
)
2
a
θ
)
=0.105.(2k+1).
+3.63
),
0
=24.2°
2
=31.7°
2
6
18
6
18.4
0
11.5
0
12.1
λ
a 2
32
31.7
24
24.2
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