lesson 1-f5 physics_a1
TRANSCRIPT
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,b. So)n" 9aves are pro$uce$ by vibrating mechanical bo$ies such as guitar strings
or a tuning or="
,c. $ater &a%es are pro$uce$ by a $isturbance ,or vibration. on a still 9ater surace"
Propa#ation *Tra%e++in#, of $a%es
" When a 9ave travels through a me$ium1 the particles o the me$ium vibrate about their
e-)i+i.ri)m positions"
)" ?o9ever1 the particles o the me$ium "o not travel in the $irection o the 9ave"
2" * 9ave transfers energy an$ the momentum rom the so)rce o the 9ave ,the oscillating or
vibrating system. to the s)rro)n"in#s"
*ctivity
To To "emonstrate that &a%es transfer ener#' &itho)t transferrin# matter
*pparatus@ Materials 4a$io1 can$le an$ matches"
Proce")re
" * can$le is place$ about ' cm rom the spea=er o a ra$io"
)" The can$le is lit an$ the movements o its lame is observe$"
2" Then1 the ra$io is turne$ on an$ the volume o the soun$ is gra$ually increase$ until a change in the
movement o the lame becomes noticeable"
Disc)ssion
The lame %i.rates 9hen the ra$io is turne$ on" This observation sho9s that the propagation o the soun$
9aves rom the vibration o the cone o the spea=er transers ener#' ,or momentum. to the lame an$causes it to %i.rate"
Conc+)sion
Waves transer energy rom a vibrating system &itho)t transerring matter"
The total energy carrie$ by a 9ave $epen$s on its amp+it)"e an$ fre-)enc'" * 9ave 9ith a large amplitu$e
or a high reAuency carries a +ar#er amount o energy"
$a%efronts in Re+ation to the Direction of Propa#ation of $a%es
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" * &a%efront is a line or plane on 9hich the vibrations o every points on it are in phase an$ are at
the same $istance rom the source o the 9ave"
)" Points in a 9ave are in phase i they vibrate in the same $irection 9ith the same $isplacement"
P+ane $a%efronts
" Figure "3 sho9s the pro$uction o plane 9ater 9aves 9hen a 9oo$en bar vibrates vertically at a
constant reAuency on the surace o the 9ater
)" Lines P%1 4S1 T# an$ BW are straight lines along the respective crests o the 9aves" These lines
are calle$ &a%efronts"
2" Figure "5 sho9s that the 9averonts are per pen"ic)+ar to the $irection o propagation"
Circ)+ar $a%efronts
" When 9e use a ingertip to touch the surace o 9ater repeate"+'1 circular 9averonts are pro$uce$
as sho9n in Figure "-"
/! The 9averont at any point is perpen"ic)+ar to the $irection in 9hich the 9ave is a$vancing
T'pes of $a%es
There are t9o types o 9aves"
,a.Transverse 9ave
,b. Longitu$inal 9ave
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Trans%erse $a%es
" * transverse 9ave is a 9ave in 9hich the vibration o particles in the me$ium is at ri#ht an#+e
,perpen$icular. to the $irection o propagation o the 9ave"
/! 8>amples o transverse 9aves are &ater &a%es an" +i#ht &a%es"
(on#it)"ina+ $a%es
" * longitu$inal 9ave is a 9ave in 9hich the vibration o particles in the me$ium is para++e+ to the
$irection o propagation o the 9ave"
)" 8>ample o longitu$inal 9aves are so)n" &a%es"
E0ercise
" &SPM'-@%2(!iagram + sho9s the cross section o 9ater 9aves"
Which o the ollo9ing statements is true about the 9ater 9avesD
* T an$ # have the same phase
/ Wave energy is transerre$ rom position S to #
C The 9avelength is the $istance bet9een S an$ #
! The particle at # oscillates in a $irection parallel to the $irection o the 9ave
propagation
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)" &SPM'-@%25(!iagram )) sho9s t9o situations 9here a ball loats an$ moves on the surace o
the 9ater"
The $irection o the movement o the ball is
* parallel to the $irection o the 9ave propagation
/ perpen$icular to the $irection o the 9ave propagation
C the same as the $irection o the 9ave propagation
! the opposite to the $irection o the 9ave propagation
2" &SPM'0@%)0(Which $iagram sho9s the pro$uction o a longitu$inal 9aveD
3" &SPM'@%)5(Which $evice is use$ to sho9 that light is a transverse 9aveD
* ;lass prism
/ !ouble slit
C !iraction grating
! Polaroi$ bloc
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5" &SPM'7@P)@%(!iagram sho9s ho9 a vibrating tuning or= pro$uces soun$ 9aves in air"
,a. #n$erline the correct ans9er in the brac=et to complete the sentence belo9"
Soun$ 9ave is a ,longitu$inal1 transverse. 9ave"& mar=(
,b. /ase$ on !iagram 1
,i. name region E1 & mar=(
,ii. mar= one $istance 9hich is eAual to a 9avelength o the soun$ 9aves"
Label the $istance using the symbol *"& mar=(
,c. The tuning or= in !iagram vibrates in 9ater"
What happens to the spee$ o soun$D& mar=(
-" &SPM'+@P)@%(!iagram sho9s a slin=y spring being move$ let an$ right continuously"
,a. Complete the sentence belo9 by tic=ing ,✓. the correct bo>"
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,b.
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T
f =
T is in%erse+' proportional to an$ vice versa"
E0ercise
" * mass on a spring oscillates 9ith a reAuency o 3 ?G" What is the time ta=en by the mass to
complete )' oscillationsD
)" * mass on a spring oscillates 9ith a reAuency o 2 ?G" Calculate
,a. the number o oscillations in ' s1
,b. the perio$ o oscillation"
2" * 9ave o reAuency )3' ?G has a 9avelength o - m" What is the spee$ o the 9aveD
Disp+acement3time 4raph of a $a%e
From the graph o s against t in Figure "'1 the ollo9ing inormation is obtaine$"
,a. *mplitu$e1 * H a cm
,b. Perio$ o oscillation1 T is the time bet9een points:
,i. ' an$ F1 ,ii. C an$ ; or ,iii. P an$ %
E0ercise
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From the graph1
,a. state the amplitu$e1
,b. calculate the perio$ o the oscillation1
,c. calculate the reAuency o the oscillation"
Disp+acement3"istance 4raph of a $a%e
1. The 9avelength1
λ
is the $istance bet9een successive points o the same phase in a 9ave" For
e>ample:
(a) the $istance bet9een t9o successive crests or t9o successive troughs in a
9ater 9ave1(b)the $istance bet9een t9o successive compressions or t9o successive
rareactions in a soun$ 9ave"
2. The S6 unit o 9avelength1
λ
is metre ,m."
E0ercise
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"
Fin$
(a) the amplitu$e1
(b) the 9avelength o the 9ave"
)" The igure sho9s the orm o a transverse 9ave pro$uce$ by a slin=y soring"
What is
,a. its amplitu$eD
,b. its 9avelengthD
Re+ationship .et&een Spee" *%,1 $a%e+en#th *
λ
, an" fre-)enc' *f,
v f λ =
E0ercise
1. The $isplacement$istance graph in Figure "3 sho9s the motion o a transverse 9ave" The source
o the 9ave pro$uces ' complete 9aves in one secon$"
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Calculate
(a)the amplitu$e1 (b) the 9avelength1 an$ (c)the spee$ o the 9ave"
)" The igure belo9 is the $isplacementtime graph o a 9ave"
Calculate
,a. the amplitu$e1
,b. the reAuency1
,c. the 9avelength1i the spee$ o the 9ave is + cm s "
2" &SPM'7@%2'(!iagram 0 sho9s a loa$ being oscillate$ on a spring"/ase$ on !iagram 01 9hich
o the ollo9ing $isplacementtime graphs represents oscillation o the loa$ rom P to % an$ bac=
to 'D
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3" &SPM'+@%)0(!iagram 7 sho9s the $isplacement$istance graph o a 9ave" The reAuency o the
9ave is 5"' ?G"
What is the velocity o the 9aveD
* 5' cm s
/ 75 cm s
C '' cm s
! 5' cm s
5" &SPM'@%)+(!iagram )) sho9s a 9ave"
The spee$ o the 9ave is 3"' m s" The $istance o 5 consecutive crests is + m"
What is the reAuency o the 9aveD
* '"3 ?G / '"5 ?G
C )"' ?G ! )"5 ?G
-" &SPM@%)0(!iagram )' sho9s soun$ 9aves pro$uce$ by a tuning or=" The velocity o the
soun$ in air is 23' ms"
What is the reAuency o the soun$ 9aveD "
* )'3"' ?G / )+2"2 ?G
C 23") ?G ! 3'+"' ?G
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7" &SPM'5@%25(The graphs sho9 the crosssections o 9ater 9aves" Which 9ave has the greatest
energyD
+" &SPM'5@%2)(The $iagram sho9s a 9averont pattern pro$uce$ by a $ipper vibrating at a
reAuency o ) ?G in a ripple tan="
What is the spee$ o the 9avesD
* ) cm s
/ +cms
C ) cms
! + cms
0" &SPM'7@%)0(!iagram + sho9s a 9ave pattern on 9ater"
Wavelength is the $istance bet9een the points
* P an$ % / P an$ 4
C % an$ S ! 4 an$ S
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