Topicmaf44e92b01654b61_1528449000663_0Topic

Standing waves

Levelmaf44e92b01654b61_1528449084556_0Level

Second

Core curriculummaf44e92b01654b61_1528449076687_0Core curriculum

VIII. Vibrating motion and waves. The student:

6) describes the mechanism of the formation and propagation of sound waves in the air; gives examples of sound sources.

Timingmaf44e92b01654b61_1528449068082_0Timing

45 minutes

General learning objectivesmaf44e92b01654b61_1528449523725_0General learning objectives

Discussing the conditions necessary to create a standing wave.

Key competencesmaf44e92b01654b61_1528449552113_0Key competences

1. Presenting the phenomenon of wave reflection.

2. Discussing the phenomenon of wave interference.

3. Presenting a standing wave as a special case of wave interference.

Operational (detailed) goalsmaf44e92b01654b61_1528450430307_0Operational (detailed) goals

The student:

- understands the phenomenon of wave reflection and interference,

- knows the conditions necessary to create a standing wave.

Methodsmaf44e92b01654b61_1528449534267_0Methods

1. Talk about new material.

2. Discussion evolving during common problem solving by a class or group.

Forms of workmaf44e92b01654b61_1528449514617_0Forms of work

1. Individual work.

2. Cooperation between student and teacher.

Lesson stages

Introductionmaf44e92b01654b61_1528450127855_0Introduction

Answer the introductory questions:

1. What is the wave?
2. What is the propagation of a wave in a resilient medium?
3. What is the sound?
4. Describe the phenomenon of wave reflectionwave reflectionwave reflection.
5. What is the wave interferencewave interferencewave interference?

Proceduremaf44e92b01654b61_1528446435040_0Procedure

The reflection of the wave:
The reflection of the wave is a change of the direction of wave propagationdirection of wave propagationdirection of wave propagation without changing the medium in which the wave propagates.

[Illustration 1]

The above figures illustrate the process of the reflection of the wave at the boundary of two media differing in their speed of propagation. In this case the reflection phenomenon is also accompanied by the partial penetration of the wave into the other medium.

[Illustration 2]

A running pulse on the string.

After reaching an obstacle, the total reflectiontotal reflectiontotal reflection from the obstacle and a change of the direction of the impulse propagation is observed.

Standing wavestanding waveStanding wave:
Standing waves may occur in limited areas. Then the first wave moving in one direction interferes the second wave reflected from the border of the area, which moves in the opposite direction. As a result of the interference of such waves (a standing wavestanding wavestanding wave) is created. Different particles of the medium in which the standing wave is present perform vibrations with different amplitudes but with the same frequency.

standing wavestanding wavestanding wave is characterized by the following terms:

- a node of standing wave is a place where the molecules of the medium do not vibrate,
- an antinode of a standing wave is the place where the molecules of the medium make vibrations with maximal amplitude.

[Illustration interactive]

Between two obstacles, a standing wavestanding wavestanding wave was created as a result of the interference of two waves with the same frequencies which run in different directions. You can see both the first, the second and the third harmonic wave.

[Slideshow]

The distance between the node and the adjacent antinode is equal to 14 length of the wave which runs in the rope, while two adjacent nodes or two adjacent antinodes are separated by 12 length of the wave.
The standing wave is in fact the vibrations of the medium, also known as normal mode. The ideal standing wave differs from the wave which moves. In the case of an ideal standing wave there is no propagation of vibrations, so there is no wavefront. The places where the amplitude of the wave reaches the maximum are called antinodes, while those in which the amplitude is always zero - the nodes of the standing wave. In case of small frequency incompatibility, the nodes and the antinodes can move. If there is some incompatibility of the amplitudes, then there is no complete quenching of vibrations in the nodes.
maf44e92b01654b61_1527752256679_0The distance between the node and the adjacent antinode is equal to 14 length of the wave which runs in the rope, while two adjacent nodes or two adjacent antinodes are separated by 12 length of the wave.
The standing wave is in fact the vibrations of the medium, also known as normal mode. The ideal standing wave differs from the wave which moves. In the case of an ideal standing wave there is no propagation of vibrations, so there is no wavefront. The places where the amplitude of the wave reaches the maximum are called antinodes, while those in which the amplitude is always zero - the nodes of the standing wave. In case of small frequency incompatibility, the nodes and the antinodes can move. If there is some incompatibility of the amplitudes, then there is no complete quenching of vibrations in the nodes.

Lesson summarymaf44e92b01654b61_1528450119332_0Lesson summary

Standing wave - a wave whose ridges and valleys do not move.
The standing wave is created due to the interference of two identical waves moving in the same direction, but with opposite turns. Usually this effect is created, for example, by applying a reflected wave to the running wave.
The standing wave is in fact the vibrations of the medium, also known as normal mode.
The ideal standing wave differs from the wave which moves. In the case of an ideal standing wave there is no propagation of vibrations, so there is no wavefront. The places where the amplitude of the wave reaches the maximum are called antinodes, while those in which the amplitude is always zero - the nodes of the standing wave. In case of small frequency incompatibility, the nodes and the antinodes can move. If there is some incompatibility of the amplitudes, then there is no complete quenching of vibrations in the nodes.
maf44e92b01654b61_1527752263647_0Standing wave - a wave whose ridges and valleys do not move.
The standing wave is created due to the interference of two identical waves moving in the same direction, but with opposite turns. Usually this effect is created, for example, by applying a reflected wave to the running wave.
The standing wave is in fact the vibrations of the medium, also known as normal mode.
The ideal standing wave differs from the wave which moves. In the case of an ideal standing wave there is no propagation of vibrations, so there is no wavefront. The places where the amplitude of the wave reaches the maximum are called antinodes, while those in which the amplitude is always zero - the nodes of the standing wave. In case of small frequency incompatibility, the nodes and the antinodes can move. If there is some incompatibility of the amplitudes, then there is no complete quenching of vibrations in the nodes.

Selected words and expressions used in the lesson plan

antinodesantinodesantinodes

balance levelbalance levelbalance level

complete quenching of vibrationscomplete quenching of vibrationscomplete quenching of vibrations

direction of wave propagationdirection of wave propagationdirection of wave propagation

nodesnodesnodes

standing wavestanding wavestanding wave

total reflectiontotal reflectiontotal reflection

wavefrontwavefrontwavefront

wave interferencewave interferencewave interference

wave reflectionwave reflectionwave reflection

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wave reflection1
wave reflection

odbicie fali

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wave interference1
wave interference

interferencja fali

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direction of wave propagation1
direction of wave propagation

kierunek rozchodzenia się fali

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total reflection1
total reflection

całkowite odbicie

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standing wave1
standing wave

fala stojąca

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nodes1
nodes

węzły

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antinodes1
antinodes

strzałki

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complete quenching of vibrations1
complete quenching of vibrations

całkowite wygaszenie

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wavefront1
wavefront

czoło fali

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balance level1
balance level

położenie równowagi

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