Course: Enghlish For Physics
Waves
Supervisor
TS. Phan Thị Kim Loan
Student:
Nguyễn Hoàng Huy B1300564
waves
Introduction
Paragraph
Focus on the reading
Comprehension reading
Multiple choice
Translate into English
Exercises
Types of Waves

Mechanical waves need a material medium through which they can travel as they transfer energy. Some example of mechanical waves are water waves, sound waves, and the waves that travel along a spring or rope. The behavior of most mechanical waves can be readily observed. The material through which the energy of a mechanical wave is transferred from one particle to another is called a medium.
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Electromagnetic waves are a large and important family of waves. They need no medium through which to travel. Electromagnetic waves consisting of seven basic types: radio waves, micro waves, infrared rays, visible light, ultraviolet, X rays and gamma rays.
Mechanical waves can be classified by the way in which they displace matter. There are three general types of wave-transverse waves, longitudinal waves, and surface waves


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Surface waves have characteristics of both transverse and longitudinal waves. Surface waves cause particle in the medium to move both horizontally and vertically as the wave moves across the surface. Water waves are example of surface waves.

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Wave Characteristics: Frequency, Wavelength, Amplitude and Wave speed

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The amplitude, A, of a wave is the distance from the centre line (or the still position) to the top of a crest or to the bottom of a trough. Amplitude is measured in metres (m). The greater the amplitude of a wave then the more energy it is carrying.
The wavelength, λ, of a wave is the distance from any point on one wave to the same point on the next wave along. (The symbol is a Greek letter, `lambda`.) To avoid confusion, it is best to measure wavelength from the top of a crest to the top of the next crest, or from the bottom of a trough to the bottom of the next trough. Wavelength is also measured in metres (m).


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The frequency, f, of a wave is the number of waves passing a point in a certain time. We normally use a time of one second, so this gives frequency the unit hertz (Hz), since one hertz is equal to one wave per second.
Don`t get confused with this quantity frequency. It is not a distance travelled by waves, nor is it a speed, although it is linked to both of these quantities. For water waves and sound waves the unit hertz is usually good enough but radio and TV waves have such a high frequency that the kilohertz (kHz) or even the megahertz (MHz) are better units.
1 kHz = 1,000 Hz
1 MHz = 1,000,000 Hz

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The speed (or sometimes you might see it called velocity) of a wave, v, is how far the wave travels in a certain time. The speed of a wave depends upon the properties of the medium through which the wave is traveling. Wave speed is measured in metres per second (m/s).
The velocity of a wave can be found by calculating the product of the frequency and the wavelength.


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Nodes, antinodes, and Standing Waves

Suppose two pulse have identical shapes but equal and opposite amplitude and move toward each other in a medium. When they meet, there will be a point in the medium that is completely undisturbed at all time. This point is called a node.

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Consider two pulses with identical shapes and amplitudes traveling in opposite direction in a medium. When the pulses meet, there will be a point in the medium that has a displacement equal to the sum of the two amplitudes. This point of maximum displacement is called an antinode. The antinoted is produced by constructive interference.

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If one end of a string is connected to a vibrating source and the other end is attached to a fixed point, the string will be set into motion causing periodic wave trains. Two wave trains are produced: one by the vibrating source and the other by reflection of the original wave from the fixed end of the string. If there is no energy loss, the two wave trains will have identical amplitudes and wavelength, but will be traveling in opposite directions. The reflected wave returns to the source, constructive and destructive interference will occur producing stationary antinodes and nodes. The string will appear to be vibrating in segments. This is called a standing wave. Standing waves are example of resonance.

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Diffraction and Interference of Waves
Diffraction is the bending of a wave around obstacles placed in its path. Diffraction may be observed in a ripple tank by placing a small barrier in the path of parallel waves. The waves bend around the edges of the barrier, producing circular waves.
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Figure 1. Diffraction of Waves

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Interference is a phenomena that occurs when two waves meet each other. There are points where they reinforce as well as points they cancel each other out completely.
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Figure 2. Interference of Waves
1. Sound sources is objects emit oscillating sound.The …..(1)….. frequency of the source as well as the frequency of the wave.

2. These oscillations have frequencies from 16Hz to 20000Hz called oscillator negative. Wave have frequency in that region called….(2)…..
oscillation
sound wave.
2. Working With Vocabulary



Fill in the blank with each of the following given words. Each word is used once









Determined frequencies oscillation Ultrasound temperature
sound wave Wavelength vacuum velocity sound insulation
3. Mechanical waves with frequencies greater than 20000Hz is called….(3)….

4. Mechanical waves with …….(4)……. less than 16Hz called infrasound.

5. Musical sound is …….(5)……. frequency sound,noise is sound with a frequency not determined.
ultrasound
frequencies
determined
2. Working With Vocabulary





Determined frequencies oscillation Ultrasound temperature
sound wave Wavelength vacuum velocity sound insulation


6. Sound waves transfer in solid medium, liquid and gas. Sound waves are not transmitted in ….(6)……

7. Sound velocity dependent elasticity,density environments the ambient ….(7)….

.
temperature .
vacuum.
2. Working With Vocabulary





Determined frequencies oscillation Ultrasound temperature
sound wave Wavelength vacuum velocity sound insulation



8. In an environment, sound transmission with a determined speed. When sound transmission from environment to environment other, the sound ….(8)…. change, the ……9)……. of the sound waves change the frequency of the sound was not change.
9. Hardly transmits sound through the porous material like cotton wool they are called ….(10)….
2. Working With Vocabulary
Insulation.
velocity
wavelength





Determined frequencies oscillation Ultrasound temperature
sound wave Wavelength vacuum velocity sound insulation

3. Comprehension reading

……Electromagnetic waves have six basic waves : radio waves, gamma rays, ultraviolet, infrared rays, X rays and micro waves.
2. ……Longitudinal waves and surface waves are Mechanical waves.
3. ……A node is a point along a standing wave where the wave has maximum amplitude.
F
T
F
Decide whether each of the following statements is true (T) or false (F)

3. Comprehension reading

4. …… As the wavelength of a wave in a uniform medium increases, its frequency will remain the same.
5. …… In longitudinal waves, the vibrations are along the same direction as the direction of travel.
6. ……The amplitude of a wave is the distance from the top of a crest to the bottom of a trough.
T
T
F

3. Comprehension reading

7. ……The speed of a wave is properties to the properties of the medium through which the wave is traveling.
8. ……The distance between two successive crests is one wavelength, λ.
9. ……The antinoted is produced by constructive diffraction and interference of waves.
10. ……Mechanical waves don’t need a material medium through which they can travel as they transfer energy.
F
T
T
F
4. Multiple choice

Select the option that most closely matches your answer


1. The time needed for a wave to make one complete cycle is called the wave’s
a. Frequency
b. Period
c. Wavelength
d. Amlitude
2. Your amplifier is playing a 200 Hz tone. When you double amplitude (loudness), happens to the speed the sound (v) and the frequency:
a. v doubles, f stays the same.
b. v doubles, f also doubles.
c. v and f both stay the same.
d. v and f both decrease.
3. Frequency is measured in units called:
a. Amps.
b. Hertz.
c. Nodes.
d. Antinodes.
4. Multiple choice

4. Interaction between two waves that meet is called:
a. Reflection.
b. Refraction.
c. Diffraction.
d. Interference.

5. The speed of a wave depends on:
a. Frequency.
b. The medium.
c. Wavelenght.
d. Both a,b,c.
4. Multiple choice

6. Standing wave occurs when:
a. High frequency wave meets a low frequency wave.
b. The incident wave moves into a new medium.
c. The medium is standing still.
d. There is interference between new and reflected waves.
7. What does waves carry from place to place?
a. Energy, but not matter.
b. Energy and matter.
c. Matter, but not energy.
d. Neither energy nor matter.
4. Multiple choice

8. Which formula represented relationship between wave speed v, wavelength , frequency f and period of the wave:
a.

b.

c.

d.
4. Multiple choice

5.Translate into English

 The equation v=λ/T tell us that the wave speed is one wavelength per period; the wave moves a distance of one wavelength in one period of oscillation.

1. Ba loại sóng chính là: sóng cơ, sóng điện từ và sóng vật chất.
 Waves are of three main types: mechanical waves, electromagnetic waves and matter waves.
2. Phương trình v=λ/T nói rằng tốc độ sóng là một bước sóng mỗi chu kỳ; sóng chuyển động một khoảng cách của 1 bước sóng trong 1 chu kỳ dao động.
5. Translate into English

 Interference is a phenomenon that occurs when two waves meet each other. There are points where they reinforce as well as points they cancel each other out completely.
3. Hiện tượng giao thoa là hiện tượng hai sóng kết hợp khi gặp nhau thì có những điểm ở đó chúng luôn luôn tăng cường lẫn nhau, có những điểm ở đó chúng luôn luôn triệt tiêu nhau.
5. Translate into English
4. Các đặc trưng của một sóng hình sin là: Biên độ của sóng, chu kỳ của sóng, tốc độ truyền sóng, bước sóng và năng lượng sóng.
 The characteristics of a sine wave are: The amplitude of the wave, the wave cycle, the speed of propagation, wavelength and wave energy.
5. Sóng âm là những sóng cơ truyền trong các môi trường rắn, lỏng, khí.
 Sound waves are mechanical waves transmitted in the environment of solid, liquid and gaseous.

The velocity of sound transmit in air is: vkk = 330 m/s
The velocity of sound transmit in water is: vn= 1435 m/s
Wavelength of sound transmit in air is: λkk=50 cm
Wavelength of sound transmit in water is: λn
6 Exercise
1. Sound velocity in air is 330m/s, in water is 1435m/s. A sound having a wavelength in air is 50cm while in water how much is wavelength?
6. Exercise
The same kind of wavelength of sound propagating through different media the frequency f unchanged, so the signature will not change.
We have:
Therefore, wavelength of sound propagating in water is 217,42 cm
6. Exercise
2. A person to stroked with an axe in railways. That way 1056m, just another person to put one’s ear to the railways heard a knocked apart three seconds. To know velocity of sound transmit in air is 330 m/s. How much is velocity transmission in iron?
Stretch of road sound transmit: S = 1056m
Time heard two knocked:Δt = 3s
Velocity of sound transmit in air is: vair=330m/s
Velocity of sound transmit in iron is: vfe

Time of sound transmission in iron is:
Because sound transmission in iron faster sound transmit in air:
Velocity of sound transmit in iron is:
The answer
6. Exercise
6. Exercise
3. A horizontal wave form sinusoidal transmit on a rope air positive direction of Ox, with wavelength is 10cm, frequency is 400 Hz, amplitude is 2cm and frist phase at O is 0
a. write equation of wave
b. determine transmission velocity of wave
Wavelength: λ=10 cm
Frequency: f=400 Hz
Amplitude: A= 2cm
First phase at O is 0
6. Exercise
The answer
a. Equation of wave have formit
We have:
Therefore:
b. Velocity transmission wave:
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The end