Q: How do the particles of the medium move when a wave passes through them? A: The particles of the medium just vibrate in place. As they vibrate, they pass the energy of the disturbance to the particles next to them, which pass the energy to the particles next to them, and so on. Only the energy of the wave travels through the medium.
There are three types of mechanical waves: transverse, longitudinal, and surface waves. They differ in how particles of the medium move. You can see this in the Figure below and in the animation at the following URL. Q: How do you think surface waves are related to transverse and longitudinal waves? A: A surface wave is combination of a transverse wave and a longitudinal wave.
They differ in how particles of the medium move when the energy of the wave passes through. At the following URL, read the short introduction to waves and watch the animations. Then answer the questions below. The article gives a dictionary definition of wave. What is the most important part of this definition? What happens to particles of the medium when a wave passes? What is the medium of a mechanical wave? List three types of mechanical waves.
If you shake one end of a rope up and down, a wave passes through the rope. Which type of wave is it? Can you guess what this picture shows? The objects are guitar strings, and the moving string is the one on the bottom right. The string is moving because it has just been plucked. Plucking the string gave it energy , which is moving through the string in a mechanical wave. A mechanical wave is a wave that travels through matter.
The matter a mechanical wave travels through is called the medium. The type of mechanical wave passing through the vibrating guitar string is a transverse wave. A transverse wave is a wave in which particles of the medium vibrate at right angles, or perpendicular, to the direction that the wave travels.
Another example of a transverse wave is the wave that passes through a rope with you shake one end of the rope up and down, as in the Figure below. The direction of the wave is down the length of the rope away from the hand. The rope itself moves up and down as the wave passes through it. Q: When a guitar string is plucked, in what direction does the wave travel? In what directions does the string vibrate?
A: The wave travels down the string to the end. A mechanical wave requires an initial energy input. Once this initial energy is added, the wave travels through the medium until all its energy is transferred. In contrast, electromagnetic waves require no medium, but can still travel through one. Television can be a tremendous force for good. It can educate great numbers of people about the world around them. Television can also be an effective way to kick-start and build momentum for a campaign.
Several studies warn marketers against shifting money away from traditional mediums because in both short- and long-term strategies, television continues to be the most effective advertising medium. The disturbance could be created by the vibrating vocal cords of a person, the vibrating string and soundboard of a guitar or violin, the vibrating tines of a tuning fork, or the vibrating diaphragm of a radio speaker.
Third, the sound wave is transported from one location to another by means of particle-to-particle interaction. If the sound wave is moving through air, then as one air particle is displaced from its equilibrium position, it exerts a push or pull on its nearest neighbors, causing them to be displaced from their equilibrium position.
This particle interaction continues throughout the entire medium, with each particle interacting and causing a disturbance of its nearest neighbors. Since a sound wave is a disturbance that is transported through a medium via the mechanism of particle-to-particle interaction, a sound wave is characterized as a mechanical wave.
The creation and propagation of sound waves are often demonstrated in class through the use of a tuning fork. A tuning fork is a metal object consisting of two tines capable of vibrating if struck by a rubber hammer or mallet. As the tines of the tuning forks vibrate back and forth, they begin to disturb surrounding air molecules. These disturbances are passed on to adjacent air molecules by the mechanism of particle interaction.
The motion of the disturbance, originating at the tines of the tuning fork and traveling through the medium in this case, air is what is referred to as a sound wave. The generation and propagation of a sound wave is demonstrated in the animation below.
Many Physics demonstration tuning forks are mounted on a sound box. In such instances, the vibrating tuning fork, being connected to the sound box, sets the sound box into vibrational motion.
In turn, the sound box, being connected to the air inside of it, sets the air inside of the sound box into vibrational motion. As the tines of the tuning fork, the structure of the sound box, and the air inside of the sound box begin vibrating at the same frequency, a louder sound is produced.
In fact, the more particles that can be made to vibrate, the louder or more amplified the sound. Exploring a Hypothesis. Investigating a Question. Units of Measure. Measuring Up Metric. The Power of Per. Potential and Kinetic Energy. Work and Machines. Power to the People. Making Waves. Waves Traveling the Universe. Life Science.
Populations in Balance. Environmental Impact. Traits and Heredity. Natural Selection. The Sensational Single Cell.
Cells Teaming Up. Seeing Inside Cells. Small, Smaller, Smallest. Determining Density. Close-up Look at Change. Unit E5 Waves Traveling the Universe. Flash to Bang. Waves without a Medium. The Electromagnetic Clothesline. Making the Invisible Visible. All-Star Alien Hide and Seek. Lesson: Waves without a Medium Duration: Approximately 60 minutes Compare and contrast two kinds of waves: mechanical which require a medium of matter to move through , and electromagnetic which do not require a medium of matter to move through.
Teacher Tips The cup phone is one of the demo experiences in E4. Choose the term your students are most comfortable with and stick with it.
Some students may not respond well to the unfamiliar terminology used when describing waves. Judge whether your students would absorb the material better if you use the word "electromagnetic" or abbreviate it "EM. Make enough cup phones for students to try them out in pairs simultaneously, or allow plenty of class time for the cup phone to be passed from student to student. Remind students to pull the line of the cup-phone taut between themselves and their partners so it can function properly.
They often forget. Consider making cup phones with Styrofoam cups or paper cups instead of plastic cups, changing the type of string to yarn, or twine, or even wire or fishing line, and the length of string — students could explore whether those factors make a difference in the quality of the sound, or whether sound is carried better or not. Materials demonstration devices such as a cell phone, portable radio, laptops cup-phone s — instructions for making one are in the lesson plan for E4.
Why do electromagnetic signals and lots of other phenomena get weaker with distance? How are digital signals a more reliable way to encode and transmit information than analog signals? Teaching Notes. Setting the context: What waves are there? Possible answers: earthquake infrared microwaves ocean radio seismic sound tsunami ultraviolet visible light water x-rays.
Distinguish electromagnetic from mechanical waves 10 minutes. Paraphrase: Waves exist all around us. They could jot down the following: type of wave mechanical or not new vocabulary words such as "light year" Note that the speaker used to illustrate sound waves is only generating sound waves: this video is a physical representation of something that is often invisible to the human eye.
Review the simplest "telephones" 10 minutes.
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