Difference between revisions of "Apps-On-Physics/C2/Sound-waves/English"

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'''''λ=4L/n'''''
 
'''''λ=4L/n'''''
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|| Mathematically we can write this as,
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|| Mathematically we can write,
  
 
'''L = n by 4 of lambda'''
 
'''L = n by 4 of lambda'''
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|| As an assignment
 
|| As an assignment
  
−
Change the length of the tube to 8 metre.
+
Change the length of tube to 8 metre.
  
 
Calculate the wavelength and frequency for different vibrational modes.
 
Calculate the wavelength and frequency for different vibrational modes.

Revision as of 12:51, 19 November 2019

Visual Cue Narration
Slide Number 1

Title Slide

Welcome to the spoken tutorial on Sound Waves.
Slide Number 2

Learning Objectives

In this tutorial we will demonstrate,

Standing Wave and Standing Longitudinal Waves Apps.

Slide Number 3

System Requirements

Here I am using,
  • Ubuntu Linux OS version 16.04
  • Firefox web browser version 62.0.3
Slide Number 4

Pre-requitsite

https://spoken-tutorial.org

To follow this tutorial learner should be familiar with Apps on Physics.

For the pre-requisite tutorials please visit this site.

Slide Number 5

Learning Goals

Using these Apps we will,
  • Demonstrate the formation of a standing wave.
  • Explain the formation of nodes and antinodes.
  • Demonstrate harmonics of a standing wave.
Slide Number 6

Learning Goals

Calculate the wavelength and frequency of standing waves.
Slide Number 7

Link for Apps on physics

https://www.walter-fendt.de/html5/phen/

Use the given link to download the Apps.
Point to the file in the Downloads folder I have downloaded the Apps to my Downloads folder.
Right-click on standingwavereflection_en.htm file.

Select option Open With Firefox Web Browser option.

Right-click on standingwavereflection_en.htm file.

Select the option Open with Firefox Web Browser.

Standing Wave App opens in the browser.

Point to the radio buttons,

Reflection from a fixed end and Reflection from a free end.

In the green panel under Reflection we have two radio buttons.
  • from a fixed end and
  • from a free end.
Point to Reflection from a fixed end. By default Reflection from a fixed end is selected.
Point to Reset and Start button. Below these radio buttons you can see, Reset and Start buttons.
Point to Start >> Pause >> Resume. Start button is a toggle for Start, Pause and Resume.
Point to the three check-boxes

ncidenting wave

Reflected wave and

Resultant standing wave.

At the bottom of the green panel you can see
  • Incidenting wave
  • Reflected wave and
  • Resultant standing wave check-boxes.
Point to the check-boxes. These check-boxes are selected by default.
Click Start button. Click on the Start button.
Move the cursor to show oscillations on the string. On the yellow panel, observe the propagation of a wave in a string.


The red wave is the Incidenting wave.

Point the cursor to show the reflection from the fixed end.


Point to the blue Reflected wave.

The blue wave is the Reflected wave.


Observe that the reflected wave has a phase change of 180 degrees.

Point to show the amplitude. Here the incident and reflected waves have the same amplitude.
Uncheck the Reflected wave. Let us uncheck the Reflected wave.


If we uncheck any of the check-boxes, we cannot see the corresponding wave.

Click on the Reflected wave check-box Click the Reflected wave check-box to make it visible again.
Click on the Pause button. Click on the Pause button to stop the propagation of the waves.
Point to the resultant wave. Here is the resultant standing wave.

Pause the App when it shows this image.

This wave is formed due to the superposition of incident and reflected waves.


The resultant wave is the constructive superposition of the waves.

Cursor on the waves. Now I will show the superposition of waves in a step-by-step manner.
Click on Single step radio button.

Point to the animation after clicking.

Click on the Single steps radio button to show the animation step-by-step.
Click on the drop down to see the different time period.


Point to T/8.

Below the Single steps radio button, a drop down to show various time periods is seen.


By default it is T by 8.


We will leave it as it is.

Click 3 times on Resume button.

show Constructive and destructive interference of sound waves.

Now click the Resume button three times to show different superpositions.
Click on the Resume button and bring it to Destructive interference. This is destructive interference of sound waves.


Here the waves are out of phase.

So they subtract each other and form a straight line.

Click on Resume button. Click on Resume button again.
Point and show the intermediate superposition. This is an intermediate superposition of waves.


It lies between the constructive and destructive superposition.

Click on Resume button. Again click on the Resume button.
Point to the wave. This is constructive interference of the waves.

Here the amplitude of the resulting standing wave is, sum of both incident and reflected wave.

Continuously click on Resume button to show the three steps. For the time period T by 8, one cycle takes three steps to complete.


T by 8 means 1/8th of the total time period.

Select T/24 from the drop down.

Click on the Resume button


point to various superpositions.

Let us select T by 24 from the drop-down.


Click on the Resume button continuously to see various superpositions.


Observe that one superposition cycle now takes five steps.

Select T/4 and T/12 options >> click Resume button. You can try other options given in the drop-down on your own.
Point to N and A. After the reflection from the fixed end, you can see A and N on the string.
Point to N and A. Here N is a Node and A is an Antinode.
Slide Number 8

Node and Antinode

  • Node is the point where the particles do not have any motion.
  • Antinode is the point where the particle oscillates with maximum amplitude.
Let us define a Node and an Antinode.


  • Node is the point where the particles do not have any motion.


  • Antinode is the point where the particle oscillates with maximum amplitude.
Slide Number 9

Assignment

Using Reflection from free end option, show the formation of standing waves.


Observe the reflection by selecting various time period options.


Explain your observation.

As an assignment

Using Reflection from free end option, show the formation of standing waves.


Observe the reflection by selecting various time period options.


Explain your observation.

Let us move on to Standing longitudinal wave App.
Right-click on standinglongitudinalwaves_en.htm file.

Select Open with Firefox Web Browser.

To open the App right-click on standinglongitudinalwaves_en.htm file.

Select the option Open with Firefox Web Browser.

Point to the App. The App opens in the browser.
Highlight the 1st line from the paragraph. Here is the information related to the App interface.
Scroll down to see the interface. Scroll down to see the interface completely.
Point to the tube.


Point to the blue points.

This interface shows a tube filled with air molecules.


The blue dots inside the tube represent the air molecules.

Point to both the graphs in given sequence. Here we can see two plots.

Displacement of particles and Divergence from average pressure.

Point to both the X- axis.

Point to Δx.

Point to Δp.

X axis represents the length of the tube.


Δ(delta)x is the change in displacement of molecules from the equilibrium position.


Δ(delta)p is the Divergence from average pressure.

Point to pink and red waves. Observe the pink and red waves.

They show the instantaneous movement of air molecules.

Point to the Form of tube and move the cursor to show the different radio buttons. In the green panel, under the heading Form of tube, we have three radio buttons.
Point to the default selected form. By default both sides open radio button is selected.
Point to the Vibrational mode.

Point to Lower and Higher buttons.

Next, under Vibrational mode we see two buttons, Lower and Higher.
Point to the Lower buttons.


Point to show the fundamental.

By default, the App shows the lowest Vibrational mode.


The lowest vibrational mode of the system is known as fundamental.


Fundamental vibrational mode is the first harmonic followed by the higher harmonics.

Point to Length of tube edit box. We can change the Length of the tube in this box.
Point to Length of tube. Length of the tube can be varied between 1 meter to 10 meters.
Point to Wavelength and Frequency. The App calculates the Wavelength and Frequency based on the length of the tube.
Click on the Higher button till we get a 5th overtone. Click the Higher button continuously to show 5 overtones for the six harmonical vibrations.
Click on F5 key. Click on F5 key on the keyboard to reset the App.
Point to the tube.

Move the cursor to show the particles at the middle.

Move the cursor to show the particles at extreme positions.

Observe the motion of air molecules.

Molecules in the middle of the tube do not displace from the mean position.

Therefore in the Displacement of particles graph, node is in the middle.

Show the movement of particles and then point to the graph Observe that particles at the extreme positions are oscillating in and out.

Here particles oscillate with maximum amplitude.

Therefore antinode is present at the extreme ends of the X- axis.

Move the cursor to 2nd graph. Let us move to the second graph.
Cursor on the interface. Observe the movement of particles inside the tube and graph simultaneously.
While editing point to graph and the tube. In the graph, movement of the pink wave shows the changes in the pressure.

As the particles move towards the center, they get compressed, so pressure increases.

When they move away pressure decreases.

Click on one side open Form of tube radio button. Under Form of tube, select one side open radio button.
Cursor on the tube. Observe the movement of particles in this form of the tube.
Point to the closed end. Here particles at the closed end are not moving.

Therefore the pressure is maximum at this end.

Cursor on the interface. Let us calculate the wavelength in this form of the tube.
Define Wavelength in a text-box.

show the picture for which we have to calculate the wavelength.


First let us define wavelength.

Wavelength is the distance between two consecutive peaks.

Click on the Higher button.

Point to the 1st overtone

Click on the Higher button to show the first overtone.

We have to calculate the wavelength of first overtone wave.

Slide Number 10

Wavelength


L = (n/4)x λ

L is length of tube

λ is wavelength

n= 1,2,3,......n


λ=4L/n

Mathematically we can write,

L = n by 4 of lambda


here L is length of the tube and lambda is the wavelength.

‘ n’ can take values from 1 to n.

By rearranging the equation we can write this as

lambda= 4L upon n

Slide Number 11

Wavelength


λ=4L/n


λ=(4 X 1)/3= 1.33 m


Now to calculate the wavelength, observe that the first overtone wave is three-fourth of the complete wave.

Here the value of n is 3.

From the App, value of length of tube can be taken as L.

Therefore the calculated value of wavelength is 1.33 metre.

This is the wavelength of first overtone mode of vibration.

Slide Number 12

Frequency

The number of complete oscillations per second is known as the frequency of a sound wave.

It is measured in hertz (Hz).

f=c/λ

λ is wavelength

c is speed of sound wave

Now we will calculate the frequency of the wave.

The number of complete oscillations per second is the frequency of a sound wave.


It is measured in hertz (Hz).


Frequency is calculated using the formula.

f=c/λ

λ' is wavelength and

c is speed of sound wave

Point to the value in the App. The App has given the value for speed of sound wave as 343.5 metre per second at 20 degree Celsius.
Cursor to show the wave for which frequency has to be calculated. Let us calculate the frequency of the same wave.
Show the picture

f=c/λ

=343.5 / 1.33

= 258.27 Hz

Substitute the values for the above formula from the App.

The value for the frequency is 258.27 Hertz.

This value is comparable to the value shown in the App.

Slide Number 13

Tabular Column

Let us make a tabular column to show the wavelength and frequency for 6 harmonical modes.
Click on Higher. Click on the Higher button to go to next harmonic.
Slide Number 14

Tabular Column

Show the tabular column with values

Similarly I have calculated the values of frequency and wavelength for higher harmonics.
Slide Number 15

Assignment

Show the empty table.

As an assignment

Change the length of tube to 8 metre.

Calculate the wavelength and frequency for different vibrational modes.

Slide Number 16

Assignment

Change the Form of tube to both sides closed and explain the graphs.

Another assignment.

Change the form of tube to both sides closed and explain the graphs.

Slide Number 17

Summary

Let us summarize.

Using these Apps we have,

  • Demonstrated the formation of a standing wave.
  • Explained the formation of nodes and antinodes.
  • Demonstrated harmonics of a standing wave.
Slide Number 18

Summary

Calculated the wavelength and frequency of standing waves.
Slide Number 19

Acknowledgement

These Apps were created by Walter-fendt and his team.

These Apps were created by Walter-fendt and his team.
Slide Number 20

About the Spoken Tutorial project.

The video at the following link summarizes the Spoken Tutorial project.

Please download and watch it.

Slide Number 21

Spoken Tutorial workshops.

The Spoken Tutorial Projectteam conducts workshops and gives certificates.

For more details, please write to us.

Slide Number 22

Forum for specific questions:

Do you have questions in THIS Spoken Tutorial?

Please visit this site

Choose the minute and second where you have the question.

Explain your question briefly.

Someone from our team will answer them.

Please post your timed queries in this forum.
Slide Number 23

Acknowledgement

Spoken Tutorial Project is funded by MHRD, Government of India.
This is Himanshi Karwanje from IIT-Bombay.

Thank you for joining.

Contributors and Content Editors

Karwanjehimanshi95, Madhurig, Nancyvarkey, Snehalathak

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