Đề thi học sinh giỏi vật lý lớp 12 số 2

SỞ GD&ĐT NGHỆ AN
(Đề thi có 01 trang)
KỲ THI CHỌN HỌC SINH GIỎI TỈNH LỚP 12 THPT
NĂM HỌC 2012 – 2013
Môn thi: VẬT LÍ 12 THPT - BẢNG B
(không kể thời gian giao đề).
Câu 1 (5,0 điểm).
 !"#$%&'()
#*+,-./01')$'23456.57'89':;<=
>3?@7ABC#,@
D
E.'F.G/HGI('9*$/-J%
?/0?'(KLM1')$!KN.G/HOP$Q34M5
R.!S#TJ.
).4'('Q3..FM/4'(6.
D':GI('9U$2)U.>3V'.''"
'F':'&W
UF:3)X'-6740R7'8L
*H'(5.!6.N.G/HGI('9$W
Câu 2 (5,0 điểm).
/RB=&3-7@& F"Y$<73D4'(.5M
/
Y <
3 D@D ST$3 D@SD  TST
= π = π + π
!'(/3CQ@&.#$Z,@R'(
@& ['\
FM/@&9':]/RB=7Y$<]Y#^$]<#D
D$_':/RB=@Y<_`&Y_#a7'G@!
':4'(X'9/R'9Y<.'9<_W
U]

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D
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'(6]
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D
W
*c?d/3':6'9_a7'G':+/R_2dB4'(X'9W
Câu 3 (5,0 điểm). '99CQ3DE.'23Y$<'b7CQ3
Y<
3  D @S  TST
D
π
= π −
<F3(4OC&

A SeT$/ DS T
U
= = Ω
π
f0'b&
*
U
 SgT
D
−
=
π

fF/Nh
EQ3ihP

h jS T= Ω

F:3)'(4'b>39
F:3)'b7
]<
3
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DEQ3ihP
D
h
':[@3BR30/R'99Y<X'9
D
h
W
Câu 4 (3,5 điểm).
](.@71$=Y<'"'/R/0H..3[&.5/0H/5(B3
HO J& H5P,U.k.G/H'23$`.!'G$4G3C:B3
H('94?L/0HSlH'23'!.5.TJP,D.
R3X6B3 HW
Dm6.4G3C:'9PR3W
Câu 5 (1,5 điểm).
](4OC'-$' H4#$D&6(5@M7'b='">3B+
.F@73':9(!4OC4$&Q34.' H_#4'b
&'(d

#Y9C>3!4OC$@3'&7'234OC6! =3-eVC7'G'b
"3C:>3!4OC :k'23'bWF'b/N@3B6'-

j
$n S T
−
ρ = Ω

- - - Hết - - -
Họ và tên thí sinh Số báo danh 
Đề chính thức
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e

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h
eD
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SỞ GD& ĐT NGHỆ AN KỲ THI CHỌN HỌC SINH GIỎI TỈNH LỚP 12 THPT
NĂM HỌC 2012 - 2013
HƯỚNG DẪN CHẤM ĐỀ THI CHÍNH THỨC
][ VẬT LÍ 12 THPT - BẢNG B
SHướng dẫn chấm gồm 04 trangT
Câu Y N9i dung Đi<m
1.
(5,0đ)

o<I('9



 D$ST

∆ = =
 $D
N.G/H&?'(L'G3dd+3M
$$

S  T  ∆ − − =
$$ $$ D

    

⇔ − = ⇔ = − = −ω

C.4'('Q3&

DS/4 , @T

ω = =

$n
pM/4'(&49
 Y@S  T
= ω + ϕ
$
.  Y@S  T⇒ = = −ω ω + ϕ
9#
 


 Y@   D
. Y @ 
= ϕ = ∆ − ∆ = −


= − ω ϕ =

Y D
S/4T
=

⇒

ϕ = π

$n
CM/4'(
 D@SD TST
= + π
 $D
D
?'(GI
q
 
   ST= ∆ − ∆ = −
$3 
D
 S@T

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r n*Y UnST
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− + π
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q

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D D
. Y  D UST= ω − =
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2.
(5,0đ)
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] D]
D 4 D 4
3  @S  Tf3 @S  T
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λ λ
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.
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3 3 3 D@ S4 4 T @  S4 4 T
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   
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   

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]
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⇒
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⇒ ⇔
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λ
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]
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λ
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Y<
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
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
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Y< Y<
4 4 S T S T DY< *
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* *
4 4 
U
+ = =
λ
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*
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D U D U
U D

4  4 S  T
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+
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 UDD$n  D$nUST
^
= ⇒ ≈
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$D
3.
(5,0đ)
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&
A  
  D
v A S Tfv S T$h h jS T


U U
= ω = Ω = = Ω = = Ω
ω
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D D
 A 
D
v Sh /T Sv v T S T
U
= + + − = Ω

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U
K
+
d 
_
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Y
E(b`3
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A 
v v

 S/4T
h / Z
U

−
π
ϕ = = − ⇒ ϕ = −
+
 $n
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3   3
S/4T
U
π
ϕ = ϕ −ϕ ⇒ ϕ = ϕ −ϕ = −
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

z
Z
d SYT
v D
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Z
 @S  TSYT
D U
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D D D
]<  A ]<  ]<
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v Sh /T v S T z d v D DST
U
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]<
@.5
A
]< ]<
v 
 S/4T
h / Z
U
π
ϕ = = ⇒ ϕ =
+
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3S]<T ]< 
S/4T
Z U Z
π π π
ϕ = ϕ + ϕ = − = −
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]<
3 D D @S  TST

Z
π
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D D
D
D
D D
A 
A 
z Sh /T z
p d Sh /T
Sv v T
Sh /T Sv v T
Sh /T
h /
+
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+ + −
+ +
+
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D
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Sh /T h / v v
h /
−
+ = ⇒ + = −
+
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D A 
h v v /= − − =

DS T Un$nS T
U
− Ω ≈ Ω
 $D
4.
(3,5đ)
 J@3 4G3C:& H5=MRB3 H'V4G3C:
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$n
r!&'9J'23
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
u 

y
u 4 D
= =
−
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D
D
u 
y
u 4 U
= =
−
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kST$SDT.SUT@3C/u#tST $n
D
&

4 ST=
$
D
4 DST=
q
q

 

4
y 4 ST
4

= − ⇒ = −
f
q
q
D
D D
D
4 D
y 4 ST
4 U
= − ⇒ = −
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q q q
D D  
D
4 S4 4 T S4 4 T ST
U
∆ = + − + =
 $
5.
(1,5đ)
y'b$/!4OC3Bb@3B'b'(XJL

4'&&4
'b>3!4OC

L
d
h

=
Eb"3C:>3!4OC/
>∆
#d

∆
#

L
 
h
∆

$D
5
D 

L > >
 h h
φ − φ∆φ ∆φ
= − ⇒ ∆ = − ⇒ ∆ = −
∆
$D
*
D
φ
k[>3!4OC d#@3C/
D
φ
#


φ
k[>3!4OC d#d

@3C/
 
Adφ =


Ad
>
h
⇒ ∆ =
ST
$D
E!.5(!4OC
 4
DN
S
N
L
22
0
2
0
π
µ=µ=
SDT
] 7'b/N!4OC
2

d
4
S
R
π
′
ρ=
′
′
ρ=

SUT
$D
CSDT.SUT.ST'"
∆
0
2222
0
I
16
DdN
q

′
ρ
π
µ=
S*T
5Q344OC
DNπ=

′

(5)$Q34!4OC
Nd=
(6)
$D
CST.SZT.S*T'"
D *
n *
 
j
_4   D 
> d *   $*  
Z Z $n 
− −
− −
−
π π× × × ×
∆ = µ = π× × ≈ ×
ρ × ×
$D
- - - Hết - - -
Chú ý: Nếu học sinh giải cách khác đúng vẫn cho điểm tối đa.
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