What Type of Wave Can Travel in a Vacuum

Section Learning Objectives

By the end of this department, you lot will be able to exercise the following:

• Define mechanical waves and medium, and relate the two
• Distinguish a pulse wave from a periodic wave
• Distinguish a longitudinal wave from a transverse moving ridge and give examples of such waves

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Teacher Support

The learning objectives in this section will help your students master the following standards:

• (7) Scientific discipline concepts. The pupil knows the characteristics and behavior of waves. The pupil is expected to:
  • (A) examine and describe oscillatory motion and wave propagation in various types of media.

Department Key Terms

longitudinal wave	mechanical wave	medium	wave
periodic wave	pulse wave	transverse wave

Mechanical Waves

What do we mean when we say something is a wave? A wave is a disturbance that travels or propagates from the place where information technology was created. Waves transfer free energy from i place to another, but they exercise not necessarily transfer any mass. Light, audio, and waves in the ocean are mutual examples of waves. Sound and h2o waves are mechanical waves; significant, they crave a medium to travel through. The medium may exist a solid, a liquid, or a gas, and the speed of the wave depends on the material properties of the medium through which it is traveling. However, light is not a mechanical moving ridge; it can travel through a vacuum such as the empty parts of outer space.

A familiar wave that you lot can easily imagine is the water wave. For water waves, the disturbance is in the surface of the water, an example of which is the disturbance created by a rock thrown into a pond or past a swimmer splashing the water surface repeatedly. For sound waves, the disturbance is caused by a change in air pressure level, an case of which is when the aquiver cone inside a speaker creates a disturbance. For earthquakes, there are several types of disturbances, which include the disturbance of Earth'south surface itself and the pressure disturbances under the surface. Even radio waves are most easily understood using an analogy with h2o waves. Because water waves are common and visible, visualizing water waves may help you in studying other types of waves, especially those that are non visible.

Water waves take characteristics common to all waves, such as amplitude, period, frequency, and free energy, which we will discuss in the next section.

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Misconception Alert

Many people think that water waves push water from one direction to another. In reality, however, the particles of h2o tend to stay in i location only, except for moving up and down due to the energy in the wave. The free energy moves forward through the h2o, but the water particles stay in one place. If you feel yourself beingness pushed in an ocean, what you feel is the energy of the wave, not the rush of water. If you put a cork in water that has waves, you will encounter that the water mostly moves it upwards and down.

[BL] [OL] [AL] Inquire students to give examples of mechanical and nonmechanical waves.

Pulse Waves and Periodic Waves

If you drop a pebble into the h2o, but a few waves may be generated before the disturbance dies downwards, whereas in a wave puddle, the waves are continuous. A pulse wave is a sudden disturbance in which simply ane moving ridge or a few waves are generated, such equally in the example of the pebble. Thunder and explosions besides create pulse waves. A periodic wave repeats the same oscillation for several cycles, such as in the case of the wave pool, and is associated with uncomplicated harmonic motion. Each particle in the medium experiences elementary harmonic move in periodic waves by moving back and along periodically through the aforementioned positions.

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[BL] Whatsoever kind of moving ridge, whether mechanical or nonmechanical, or transverse or longitudinal, can exist in the form of a pulse wave or a periodic moving ridge.

Consider the simplified water moving ridge in Figure thirteen.2. This wave is an upwards-and-down disturbance of the water surface, characterized by a sine wave pattern. The uppermost position is called the crest and the lowest is the trough. Information technology causes a seagull to motion upward and down in unproblematic harmonic motion as the wave crests and troughs pass under the bird.

Figure 13.2 An idealized ocean wave passes nether a seagull that bobs up and down in simple harmonic motion.

Longitudinal Waves and Transverse Waves

Mechanical waves are categorized by their type of motion and fall into any of two categories: transverse or longitudinal. Note that both transverse and longitudinal waves tin be periodic. A transverse wave propagates so that the disturbance is perpendicular to the direction of propagation. An example of a transverse wave is shown in Figure 13.3, where a woman moves a toy bound up and down, generating waves that propagate abroad from herself in the horizontal direction while disturbing the toy spring in the vertical management.

Figure 13.3 In this instance of a transverse wave, the wave propagates horizontally and the disturbance in the toy leap is in the vertical management.

In contrast, in a longitudinal wave, the disturbance is parallel to the direction of propagation. Effigy xiii.4 shows an example of a longitudinal moving ridge, where the woman now creates a disturbance in the horizontal management—which is the same management every bit the wave propagation—by stretching and then compressing the toy spring.

Figure 13.4 In this example of a longitudinal wave, the moving ridge propagates horizontally and the disturbance in the toy bound is too in the horizontal management.

Tips For Success

Longitudinal waves are sometimes chosen compression waves or compressional waves, and transverse waves are sometimes called shear waves.

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Teacher Demonstration

Transverse and longitudinal waves may be demonstrated in the form using a bound or a toy jump, as shown in the figures.

Waves may be transverse, longitudinal, or a combination of the two. The waves on the strings of musical instruments are transverse (as shown in Figure thirteen.5), and so are electromagnetic waves, such as visible light. Sound waves in air and water are longitudinal. Their disturbances are periodic variations in pressure that are transmitted in fluids.

Figure thirteen.5 The wave on a guitar string is transverse. Nonetheless, the sound moving ridge coming out of a speaker rattles a sheet of newspaper in a management that shows that such sound wave is longitudinal.

Sound in solids tin be both longitudinal and transverse. Essentially, water waves are also a combination of transverse and longitudinal components, although the simplified water wave illustrated in Figure 13.2 does non show the longitudinal move of the bird.

Earthquake waves under Earth'southward surface accept both longitudinal and transverse components equally well. The longitudinal waves in an earthquake are called pressure or P-waves, and the transverse waves are chosen shear or S-waves. These components have important private characteristics; for example, they propagate at different speeds. Earthquakes also accept surface waves that are similar to surface waves on h2o.

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Energy propagates differently in transverse and longitudinal waves. It is of import to know the type of the wave in which energy is propagating to empathize how it may bear upon the materials around it.

Spotter Physics

Introduction to Waves

This video explains moving ridge propagation in terms of momentum using an instance of a wave moving along a rope. Information technology also covers the differences between transverse and longitudinal waves, and between pulse and periodic waves.

Watch Physics: Introduction to Waves. This video is an introduction to transverse and longitudinal waves.

In a longitudinal sound wave, after a pinch wave moves through a region, the density of molecules briefly decreases. Why is this?

1. Subsequently a compression wave, some molecules motility frontward temporarily.

2. After a compression wave, some molecules movement backward temporarily.

3. After a compression wave, some molecules move upward temporarily.

4. After a compression wave, some molecules move downward temporarily.

Fun In Physics

The Physics of Surfing

Many people enjoy surfing in the ocean. For some surfers, the bigger the wave, the meliorate. In ane expanse off the coast of cardinal California, waves can reach heights of upward to 50 feet in sure times of the year (Figure 13.half dozen).

Figure 13.6 A surfer negotiates a steep have-off on a winter day in California while his friend watches. (Ljsurf, Wikimedia Commons)

How do waves attain such extreme heights? Other than unusual causes, such as when earthquakes produce seismic sea wave waves, nigh huge waves are caused simply by interactions between the wind and the surface of the water. The wind pushes up confronting the surface of the water and transfers energy to the water in the process. The stronger the wind, the more than energy transferred. As waves start to form, a larger surface area becomes in contact with the wind, and fifty-fifty more than free energy is transferred from the wind to the water, thus creating higher waves. Intense storms create the fastest winds, boot upwardly massive waves that travel out from the origin of the tempest. Longer-lasting storms and those storms that impact a larger area of the ocean create the biggest waves since they transfer more energy. The wheel of the tides from the Moon's gravitational pull also plays a small role in creating waves.

Actual body of water waves are more than complicated than the idealized model of the simple transverse wave with a perfect sinusoidal shape. Ocean waves are examples of orbital progressive waves, where water particles at the surface follow a circular path from the crest to the trough of the passing wave, then bike dorsum again to their original position. This cycle repeats with each passing wave.

As waves reach shore, the water depth decreases and the energy of the wave is compressed into a smaller book. This creates higher waves—an consequence known as shoaling.

Since the water particles along the surface move from the crest to the trough, surfers hitch a ride on the cascading water, gliding along the surface. If ocean waves piece of work exactly like the arcadian transverse waves, surfing would be much less exciting as information technology would only involve standing on a board that bobs up and down in place, only like the seagull in the previous effigy.

Boosted information and illustrations nigh the scientific principles behind surfing can exist found in the "Using Science to Surf Better!" video.

If nosotros lived in a parallel universe where body of water waves were longitudinal, what would a surfer's motion wait similar?

1. The surfer would motion side-to-side/back-and-forth vertically with no horizontal motion.

2. The surfer would frontwards and astern horizontally with no vertical motion.

Cheque Your Understanding

Teacher Support

Teacher Support

Use these questions to assess students' achievement of the department'south Learning Objectives. If students are struggling with a specific objective, these questions will help identify such objective and straight them to the relevant content.

i .

What is a wave?

1. A wave is a force that propagates from the place where it was created.

2. A wave is a disturbance that propagates from the place where it was created.

3. A moving ridge is affair that provides book to an object.

4. A wave is matter that provides mass to an object.

2 .

Do all waves crave a medium to travel? Explicate.

1. No, electromagnetic waves exercise non require whatsoever medium to propagate.

2. No, mechanical waves do non crave whatsoever medium to propagate.

3. Yes, both mechanical and electromagnetic waves require a medium to propagate.

4. Yes, all transverse waves crave a medium to travel.

3 .

What is a pulse wave?

1. A pulse wave is a sudden disturbance with merely i wave generated.

2. A pulse moving ridge is a sudden disturbance with merely one or a few waves generated.

3. A pulse wave is a gradual disturbance with just one or a few waves generated.

4. A pulse wave is a gradual disturbance with only one wave generated.

4 .

Is the following statement truthful or false? A pebble dropped in h2o is an example of a pulse wave.

1. False

2. True

five .

What are the categories of mechanical waves based on the type of motion?

1. Both transverse and longitudinal waves
2. Only longitudinal waves
3. Only transverse waves
4. Simply surface waves

6 .

In which direction do the particles of the medium oscillate in a transverse wave?

1. Perpendicular to the direction of propagation of the transverse moving ridge
2. Parallel to the management of propagation of the transverse wave

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