育教伊華貝三榮張七第
WAH KIU YAT PO
三期星
日五十月三年〇十九一展公年九十五園民事
BRO英文中學會考試題預習專欄
The velocity of sound in eir depends upon the】 (temperature as follows
中文中學雞
考試題預習專欄
道英文書院主編
273
英文科
王淑方。
物理科
)
PHYSICS (21)
WAVE MOTION AND SOUND
The study of the propagation of deformations through.
wave motion. A travelling. deformable hodia is known as wave is the movement of a disturbance from a soutos. The result of such a movement is the transfer of energy from the source to places around it..
from the fo
There are two types of waves:
Mechanical waves, and Electromagnetic waves,
Rechanical waves i examples: water waWORZ
spund waves, etc.
They are caused by a disturbance in a material medium. Katerial media are essential for such waves motion.
Electromagnetic wavess such as radio waves, rađaz,
waves, light waves, etc.
They are caused by a disturbance in an elec- tromagnet e field and can travel in a vacuum and in. some material media. It is essential to pin-point that material media is not essential for this wave motion.
Types of waYOU
1. Transverse Haven
The vibrations of the medium are perpendicular to the
27 Long,tion of propagation. (water wave)
«Mayen
The vibration of the medium is parallel to the direction of propagation. (Bound wave)
3. Torsional waves.
The vibrations of the medium are rotational to the direction of propagation. (not important in Form 5 syllabus)
ALL waye motions are most easily represented:" graph in which the displacement of the medium is plotted as a function of time. In case of the simplest type of vibration, the simple harmonic type the graph appears as
n.
Wave terminaology.
Amplitude, the maximum displacement produced by a wave pulse, the maximum dieplacement of partioals in a medzun from its mean position.
** wavelength, the distance between two successive
corresponding points, such as oreat to crest.
*- frequency, the number of complete waves that
pass a given point per seosad.
**** period, the time for one complete cyc
the reciprocal of frequency
the basic relation of wavo la give: д
whara w in the velocity of the wave
f is the frequency of the wave and Ads the wavelength of the wave
Reflection and retraction or waves
Havas can be reflected from houndaries between different madia. They can also be refracted, i.e. the experience a change in velocity as they pass from one medium into another medium if the elastic character and the densities of the media are different.
Principle of Superposition
Further more, wayas pass through each other without sither being altezed, each displaces or disturbs the same point by a certain amount. Their displacements are added or superimposed with the result that interference effects odour. If two similar Vaves are superimposed in such manner that they are ixactly in phase with each other, they re-inforce ons inother. But if the two waves are exactly out of
phase with each other, they interfere destructively and nullify one another. If the two similar waves of almost, but not quite, the same. frequency are superimposed, the result is the beat phenomenon, which they alternately re-inforos and destroy one another with a beat frequency of the numerical differen of their frequency, f
Stationary- or standing waves
An interesting interference phenomenon is observed when two waves exactly similar but traveliang in opposite direction and with the name speed are. "Buperimposed. The result is the standing or stationazs wave, which displays nodes, regions of no disturbance, and antinodes, regions of maximum disturbance. Sound
1. Sound is a longitudinal mechanical wave motion.
khe manzar of sound comes from the mechanical: vibration of the particles of material media.
„Sound needs material media such as solid, liquid and
gas for its transmission, Sound cannot travel "through" n TAQUUM.
Sound is produced by vibrating objects of all sorts. If the frequency of the vibration is within the range of 20 to 20,000 cycles, the sound produces is audible. This in known as the audible frequency
(where v is the velocity of sound in air
in the velocity of sound in S.T.F.
is the temperature in Centigrada .
velocity of sound at 9.7.P.
330 metres per seo.
Factors affecting the velocity of sound in siz
1. Increases as the temperature of the air inorGASSE, 2. Does not depend on the pressure of the air 3. Doss not depend on the frequency of Bound
4. Does not depend on the intensity (loudness) 5. Depends on the humidity of air
Echoes
A sound heard by reflection is called echo. Sound persiste in our ears for about 1/10 sec. In order to hear the echo of a sound, it must arrive least 1/10 second later. The minimum distance of the reflecting surface from the bounding body is 55 feet. Characteristics of sound-
The three characteristics of sound are pitoh, intensity and quality,
(1) Pich is the auditory effect of frequency. The
higher the frequency is higher is the pitch. For a normal person, sounds are audible in a frequency range of 20 to 20,000 cycles per sec (2) Intensity depends up on the energy of the sound
sourse. It depends on the amplitude of vibration, Intensity depends on the aquara of the amplitude. (3) Quality depends upon the presence of overtones,
on the presence of that is the number, pitch and intensity of the harmonies or overtones in the note. The note itself is called the fundamental tone, or firat harmonio. It is superimposed by the brended harmonies.
Vibrating Strings
A standing wave can be produced by a stretchea string. The sonometer is an instrument with a strained string of variable length and tension.
The frequency of a stretched string is invèrsaly proportional to the length of the string.
(2) The frequency of a string is proportional to the
square root of the tension.
63) The frequency of a string is inversely
proportional to the square root of the maga-per unit length.
There are the laws of vibrating strings.
Standing waves in Pipes
A pipe open at one ond and closed at the other is refered to as a closed pipe. One open at both enda in called an open pipe. A oures of sound held at the opez and of a closed pipe of length I will
produce standing waves in the pipe if its frequency and the length of the pips are such that a node can be formed at the closed end while anti-node at the open end. The longest standing wave (fundamental): that can be formed has a wave length of
Overtones with 3x, 5x, 71, ate the fundamental frequency also produce resonance. Only odd harmonica are formed,
adamental or first harmonie
first overtone or third harmonië
second overtone or fifth harmonies
third overtone or seventh harmonio
For an open pipe, however, there must be an antinode at each open and. This means that there must be at least one node between the two anti-nodes, so that the longest fundamental wavelength has to be
Harmonio overtones can also be got up in these piper. Because of symmetry, all the haraonice can be formed commencing with the fundamental (first harmonio) in open pipes, each end being the same. The frequencies the overtones are 2 x, 3x, 4x, 51, «to, the frequeno of the fundamental wavė,
لجابر
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XX
(th)
LESSON TWENTY-ONE)~
SECTION FOUR
TRANSLATION (continued)
EXERCISE 31
25-3-1970
Translate the following passage into Chineses
A small crowd had gathered round the entrance ». the park, Chan Sing crossed the road to see what waS happening. He found that the centre of attraction was an old man with a performing monkey. The monkey's tricks, he soon discovered, were in no way remarkable. so, after throwing a few coins in the dirty hat which the man had placed on the pavement, Chan Sing began to move off, along with other members of the crowd.
At this point the man suddenly let out a loud cry Everyone turned to see what had happened. The man war bending over his monkey, which now lay quite still on the pavement. He picked up the apparently lifelsas body and, holding it close to him, began to weep. A young man stepped forward from the crowd and, taking some money from his pocket, dropped it into the hat. Chan Sing and several other people did likewise, until the coins in the hat were covered with dollar notes. Meanwhile, the man continued to hold the dead monkey in his arms and seemed to take no notice of what was going on about him,⠀
EXERCISE 32
Translate the following passage. into Chinese
The party began shortly after nine, Mr. Tang, who) lived in the flat below, sighed to himself as he heard the first sings: the steady tramp of feet on the stairs; the sound of excited voices as the guests greeted one another; and the noise of the gramophone, which was turned full on.
Luckily Mr. Tang had brought some work home. from the office, with which he occupied himself for a couple of hours, thus managing to ignore with some success the party which was going on over his head. But by eleven o'clock he felt tired and was ready to go to bed, though " from his experience of previous parties he knew that it was useless trying to get to sleep. He undressed and lay) For a while on the bed, trying to read, but the noise from the room directly above his head did not allow him to concentrate on what he was reading. He found himself reading the same page over and over again. He then switched off the light and buried his head in the pillow,} in a desperate effort to go to sleep. But even so he could not shut out the noise. Finally, after what seemed hours, he switched on the light and looked at his watchs it was just after midnight.
ANSWERS TO PREVIOUS EXERCISES
EXERCISE 28
(1) (a) vicious
(b) inflicted
(c) forbears (d) tines
(e) preserves
ornately essential
genteel prevalent
The ancient Egyptians used forks for agricultural purposes.
(3) The three kinds of forks used in the ancient daya are pitchforks, hayforks and digging forks."
(4) The word 'ugly' is used to describe the wounds in
the sense of serious wound with an unpleasant look, (5) The word 'record means the written account of
matters.
(6) The idea of eating with a fork came into Europe
from the East some two centuries before the first record of any table fork in England.
(7) The metal forks in Henry VIII's days were employe
only to pick up Indian preserves called 'ginger' (8) The custom of eating neat with a fork was widem
spread in Italy by the fifteenth century because the Italians were averse to having their food touched with fingers (which were not clean).
EXERCISE 29
∵镫(橘子》是一種非常普通而是我們需屐熊果實。它含有我所有數的灣新甜味兒,它不 但對健应有所辦益,同時更是一瓶年清而又安全的食品,因爲吃時要先去皮。由於面的,是以 小孩子能以它作球,更可以把果核彈向別人。再者,它的樸實無罪,甚錼人所謂。假如甘開始腐爛, (就是最好有時他也不能避免),它就去開始。而再令一方面,外表常是群英梨子,如可 ̇能在盛面關。但證(橋子,就從不能夠後它的缺點。這是跟一致的約。若你的觀察波飛,常电倒 上書醫生果的入將一個班證(橘子)放淮紙袋中
EXERCISE 30
我锌到我小村长在巴温城市之 别。看哪
!那豆冱鵟聲響!起彻。 保音破是振點欲难,但過了一小時後,我深已確度了,對我來說,每一線每物都是新羅和奇特約 坦白說,倫敦給我第一印疫並不是奈合我心意。最後,當要到達了朋友给我預定酒店時,我略 到非常安然。在一天之內,我已觀看了不少。那天晚上,我覺得最需要的便是身心的依•
EXERCISE 33
TRANSLATE THE FOLLOWING PASSAGES INTO ENGLISH. 《一萣人焓踝與者之白:腐之學,物業能階也。又耀共曰:「源之利,於物然 ∴不能我。或曰:「以于之矛陷子之盾,何如?」其入能密也。夫不可陷之堆膑無不能之
不可同性版式:
(二)應*百食之,得吗。疝曰:「千無敢食物也,天帝他我百獸,今于生我,是逆天帝命 也。于以我寫不屑,若篇子先行,于我後,觀百獸之見我不走乎。」應以為然,故鄉 與之行,厭鬼之皆走。但不知獸長記爾走也,以爲理據。
first harmonio
Fundamental
Firat overtone or second harmonie f2 - 1 - 270
Second overtone or third harmonis f3 - 27-
(Third overtone or fourth harmonis
Fourth overtone or fifth harmonis