Difference between revisions of "Apps-On-Physics/C2/Reflection-and-Refraction/English"

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−
 
 
{|border=1
 
{|border=1
 
|-
 
|-
−
|| '''Visual cue'''
+
|| '''Visual Cue'''
 
|| '''Narration'''
 
|| '''Narration'''
 
|-
 
|-
Line 15: Line 14:
 
|| In this tutorial, we will learn to,
 
|| In this tutorial, we will learn to,
  
−
Simulate reflection and refraction of a light ray.
+
'''Simulate''' reflection and refraction of a light ray.
  
 
Calculate the angles of reflection and refraction.
 
Calculate the angles of reflection and refraction.
  
−
Change the medium and angle of incidence to verify '''Snell's Law'''.
+
Change the medium and '''angle of incidence''' to verify '''Snell's Law'''.
  
 
|-
 
|-
Line 25: Line 24:
  
 
'''Learning Objectives'''
 
'''Learning Objectives'''
−
|| Calculate the value of critical angle.
+
|| Calculate the value of '''critical angle'''.
  
 
Verify '''Huygens' principle'''.
 
Verify '''Huygens' principle'''.
Line 46: Line 45:
 
|| To follow this tutorial, learner should be familiar with '''Apps on Physics'''.
 
|| To follow this tutorial, learner should be familiar with '''Apps on Physics'''.
  
−
For the pre-requisites tutorials please visit this site.
+
For pre-requisites tutorials please visit this site.
  
 
|-
 
|-
Line 54: Line 53:
  
 
'''https://www.walter-fendt.de/html5/phen/'''
 
'''https://www.walter-fendt.de/html5/phen/'''
−
|| Use the given link to download the '''Apps.'''
+
|| Use the given link to download the '''Apps'''.
  
 
|-
 
|-
 
|| Open the '''Downloads '''folder.
 
|| Open the '''Downloads '''folder.
−
|| I have downloaded the '''Apps on Physics '''to my '''Downloads''' folder.
+
|| I have already downloaded the '''Apps on Physics''' to my '''Downloads''' folder.
  
  
Line 67: Line 66:
 
|| In this tutorial, we will use,
 
|| In this tutorial, we will use,
  
−
'''Refraction of Light '''and  
+
'''Refraction of Light ''' and  
  
−
'''Reflection and Refraction of Light Waves Apps.'''
+
'''Reflection and Refraction of Light Waves Apps'''.
  
  
 
|-
 
|-
−
|| Right click on '''pulleysystem_en.htm''' file.
+
|| Right-click on '''refraction_en.htm '''file.
  
 
Select the option '''Open With Firefox web Browser''' option.
 
Select the option '''Open With Firefox web Browser''' option.
  
 
Cursor on the '''App'''.
 
Cursor on the '''App'''.
−
|| Right click on '''refraction_en.htm '''file.
+
|| Right-click on '''refraction_en.htm file'''.
  
 
Select the option '''Open With Firefox web Browser.'''
 
Select the option '''Open With Firefox web Browser.'''
Line 86: Line 85:
 
|-
 
|-
 
|| Cursor on the interface.
 
|| Cursor on the interface.
−
|| The''' App '''shows reflection and refraction of light through a given medium.
+
|| The '''App''' shows reflection and refraction of light through a given medium.
  
 
|-
 
|-
Line 109: Line 108:
  
 
|-
 
|-
−
|| Point to blue angels
+
|| Point to blue angles.
 
|| Reflection is shown by the blue coloured angle.
 
|| Reflection is shown by the blue coloured angle.
  
 
|-
 
|-
 
|| Point to black and blue angles.
 
|| Point to black and blue angles.
−
|| Observe that the angle of incidence and reflection are the same.
+
|| Observe that the angle of '''incidence''' and reflection are the same.
  
 
|-
 
|-
Line 122: Line 121:
 
|-
 
|-
 
|| Show the phenomena with the motion of the cursor.
 
|| Show the phenomena with the motion of the cursor.
−
|| When light travels from rarer medium to denser medium, it bends towards normal.
+
|| When light travels from rarer medium to denser medium, it bends towards '''normal'''.
  
 
|-
 
|-
−
|| Cursor on the green panel.
+
|| Cursor on the green '''panel'''.
−
|| On the green panel we have a choice to change a few parameters.
+
|| On the green '''panel''' we have a choice to change a few parameters.
  
 
|-
 
|-
Line 134: Line 133:
 
|-
 
|-
 
|| Click on the first drop down and change the medium to water.
 
|| Click on the first drop down and change the medium to water.
−
|| Select water as the upper medium.
+
|| Select '''water''' as the upper medium.
  
 
|-
 
|-
Line 140: Line 139:
  
 
Select air from the drop down.
 
Select air from the drop down.
−
|| Select''' '''air''' '''as the lower medium.
+
|| Select '''air''' as the lower medium.
  
 
|-
 
|-
Line 146: Line 145:
 
|| Here the ray of light travels from denser to rarer medium.
 
|| Here the ray of light travels from denser to rarer medium.
  
−
The ray bends away from the normal.
+
The ray bends away from the '''normal'''.
  
 
|-
 
|-
Line 164: Line 163:
 
|-
 
|-
 
|| Click on '''F5''' key on the keyboard.
 
|| Click on '''F5''' key on the keyboard.
−
|| Press '''F5''' key on the keyboard to refresh the '''App'''.
+
|| Press '''F5''' key on the keyboard to '''refresh''' the '''App'''.
  
 
|-
 
|-
 
|| Change the values from 0.1 degrees to 90 degrees and show the changes.
 
|| Change the values from 0.1 degrees to 90 degrees and show the changes.
  
−
Click on '''F5''' key on the keyboard to refresh and show the default value.
+
Click on '''F5''' key on the keyboard to '''refresh''' and show the default value.
 
|| Next '''Angle of incidence''' can be changed from 0.1 degrees to 90 degrees.
 
|| Next '''Angle of incidence''' can be changed from 0.1 degrees to 90 degrees.
  
−
Press '''F5 '''key to see the default value.
+
Press '''F5''' key to see the default value.
  
 
It shows 30 degrees.
 
It shows 30 degrees.
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|-
 
|-
 
|| Point below the text fields.
 
|| Point below the text fields.
−
|| Below the text fields '''App''' shows the '''Angle of reflection and refraction'''.
+
|| Below the text fields '''App''' shows the '''Angle of reflection''' and '''refraction'''.
  
 
|-
 
|-
 
|| Point to the graph.
 
|| Point to the graph.
−
|| Graph shows the angle of refraction with angle of incidence.
+
|| Graph shows the angle of refraction with '''angle of incidence'''.
  
 
|-
 
|-
−
|| Click and drag the angle of incidence.
+
|| Click and drag the '''angle of incidence'''.
  
 
Drag it slowly.
 
Drag it slowly.
−
|| We can also change the angle of incidence by dragging this red coloured ray.
+
|| We can also change the '''angle of incidence''' by dragging this red coloured ray.
  
 
|-
 
|-
Line 208: Line 207:
  
 
“n<sub>21</sub>” is the refractive index of the second medium w.r.t first.
 
“n<sub>21</sub>” is the refractive index of the second medium w.r.t first.
−
|| Before that let us state '''Snell’s law''' of Refraction.
+
|| Before that let us state '''Snell’s law''' of refraction.
  
−
Ratio of sine of angle of incidence to sine of angle of refraction is a constant.
+
Ratio of '''sine''' of angle of '''incidence''' to '''sine''' of angle of '''refraction''' is a constant.
  
−
n<sub>21 </sub>is the refractive index of the second medium with respect to first medium.
+
n<sub>21 </sub>is the refractive index of second medium with respect to first medium.
  
 
|-
 
|-
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'''Snell’s Law of Refraction'''
 
'''Snell’s Law of Refraction'''
  
−
'''Case1: '''If''' '''n<sub>21 </sub>> 1, angle of refraction is less than angle of incidence.
+
'''Case1: '''If''' '''n<sub>21 </sub>> 1, angle of refraction is less than angle of '''incidence'''.
  
−
'''Case2: '''If''' '''n<sub>21 </sub>< 1, angle of refraction is greater than angle of incidence.
+
'''Case2: '''If''' '''n<sub>21 </sub>< 1, angle of refraction is greater than angle of '''incidence'''.
 
|| Here are the 2 cases of '''Snell’s law'''.
 
|| Here are the 2 cases of '''Snell’s law'''.
  
−
1. If n<sub>21 </sub>is greater than 1, angle of refraction is less than angle of incidence.
+
1. If n<sub>21 </sub>is greater than 1, angle of refraction is less than angle of '''incidence'''.
  
−
2. If n<sub>21 </sub>is less than 1, angle of refraction is greater than angle of incidence.
+
2. If n<sub>21 </sub>is less than 1, angle of refraction is greater than angle of '''incidence'''.
  
 
|-
 
|-
Line 232: Line 231:
 
|| Change the '''Angle of incidence''' to 20 degrees.
 
|| Change the '''Angle of incidence''' to 20 degrees.
  
−
Observe that the angle of refraction has changed to 14.9.
+
Observe that the '''angle of refraction''' has changed to 14.9.
  
 
|-
 
|-
 
|| Point to the graph and values of the angles.
 
|| Point to the graph and values of the angles.
−
|| This graph shows the first case of Snell’s law.
+
|| This graph shows the first case of '''Snell’s law'''.
  
−
Here angle of incidence is greater than the  
+
Here angle of '''incidence''' is greater than the  
  
 
angle of refraction.
 
angle of refraction.
Line 244: Line 243:
 
|-
 
|-
 
|| Point to the value of refractive index of the second medium.
 
|| Point to the value of refractive index of the second medium.
−
|| Observe that the light ray bends towards the normal.
+
|| Observe that the light ray bends towards the '''normal'''.
  
 
|-
 
|-
Line 256: Line 255:
 
|-
 
|-
 
|| Point to show the refraction.
 
|| Point to show the refraction.
−
|| Notice that the light ray has bent away from the normal.
+
|| Notice that the light ray has bent away from the '''normal'''.
  
 
|-
 
|-
Line 264: Line 263:
 
|-
 
|-
 
|| Point to show Angle of refraction.
 
|| Point to show Angle of refraction.
−
|| Here the angle of refraction is greater than the angle of incidence.
+
|| Here the angle of refraction is greater than the angle of '''incidence'''.
  
 
|-
 
|-
Line 272: Line 271:
 
|-
 
|-
 
|| Point to the refracted ray.
 
|| Point to the refracted ray.
−
|| The refracted ray has bent still more further away from the normal.
+
|| The refracted ray has bent still more further away from the '''normal'''.
  
 
|-
 
|-
 
|| Change the '''Angle of incidence''' to 35 degrees.
 
|| Change the '''Angle of incidence''' to 35 degrees.
−
|| Again increase the angle of incidence to  
+
|| Again increase the '''angle of incidence''' to 35 degrees.
−
 
+
−
35 degrees.
+
  
 
In this case observe that the refraction is not possible.
 
In this case observe that the refraction is not possible.
Line 288: Line 285:
 
|-
 
|-
 
|| Cursor on the interface.
 
|| Cursor on the interface.
−
|| This phenomenon is known as total internal reflection.
+
|| This phenomenon is known as '''total internal reflection'''.
  
−
Here the critical angle is formed.
+
Here the '''critical angle''' is formed.
  
 
|-
 
|-
−
|| Point to the Critical angle.
+
|| Point to the '''Critical angle'''.
−
|| The critical angle for diamond and water is 33.3 degrees.
+
|| The '''critical angle''' for diamond and water is 33.3 degrees.
  
 
|-
 
|-
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n<sub>2</sub><nowiki>= Refractive index of the second medium</nowiki>
 
n<sub>2</sub><nowiki>= Refractive index of the second medium</nowiki>
−
|| Now we will calculate the critical angle using the formula.
+
|| Now we will calculate the '''critical angle''' using the formula.
  
 
|-
 
|-
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'''Tabular column'''
 
'''Tabular column'''
−
|| Let us make a tabular column to calculate critical angle for two different media.
+
|| Let us make a tabular column to calculate '''critical angle''' for two different media.
  
 
|-
 
|-
−
||  
+
||point to the calculated values.
−
|| Here I have calculated the critial angle for diamond and water.  
+
|| Here I have calculated the '''critical angle''' for diamond and water.  
  
 
|-
 
|-
−
|| Point to the on the interface Critical angle.
+
|| Point to the on the interface '''Critical angle'''.
 
|| The calculated value is comparable to the value shown in the '''App'''.
 
|| The calculated value is comparable to the value shown in the '''App'''.
  
Line 332: Line 329:
  
 
|-
 
|-
−
|| Change the upper medium to water and lower medium to air.
+
|| Change the upper medium to '''water''' and lower medium to '''air'''.
 
|| Next change the upper medium to '''water''' and lower medium to '''air'''.
 
|| Next change the upper medium to '''water''' and lower medium to '''air'''.
  
Line 344: Line 341:
  
 
|-
 
|-
−
|| Show the calculation''' '''for critical angle on a text-box or on a png.
+
|| Show the calculation of '''critical''' angle as image.
−
|| Then calculate the critical angle using the above formula.
+
|| Then calculate the '''critical angle''' using the above formula.
  
 
|-
 
|-
Line 366: Line 363:
 
* Note the values of refractive indices for the following media from the '''App'''.
 
* Note the values of refractive indices for the following media from the '''App'''.
  
−
* Calculate the critical angle for the two media.
+
* Calculate the '''critical angle''' for the two media.
  
 
* Compare the values with the ones shown in the '''App'''.
 
* Compare the values with the ones shown in the '''App'''.
Line 375: Line 372:
  
 
|-
 
|-
−
|| Right click on '''refractionhuygens_en.htm'''<<
+
|| Right click on '''refractionhuygens_en.htm'''.
  
 
'''Open With Firefox Web Browser'''.
 
'''Open With Firefox Web Browser'''.
Line 382: Line 379:
 
'''Open With Firefox Web Browser'''.
 
'''Open With Firefox Web Browser'''.
  
−
The''' App '''opens in the browser.
+
The '''App''' opens in the browser.
  
 
|-
 
|-
 
|| Highlight the main topic from the screen.
 
|| Highlight the main topic from the screen.
−
|| '''App''' shows '''Reflection''' and '''Refraction''' of light waves using '''Huygens''' principle.
+
|| '''App''' shows '''Reflection''' and '''Refraction''' of light waves using '''Huygen's''' principle.
  
 
|-
 
|-
Line 394: Line 391:
 
|-
 
|-
 
|| Point to the wavefront.
 
|| Point to the wavefront.
−
|| Here the plane wavefront is incident diagonally on the boundary of the media.  
+
|| Here the '''plane wavefront''' is incident diagonally on the boundary of the media.  
  
 
|-
 
|-
Line 405: Line 402:
  
 
|-
 
|-
−
|| Point to the wavefronts.
+
|| Point to the '''wavefronts'''.
−
|| Note the change in media, when the wavefront is incident on the boundary.
+
|| Note the change in media, when the '''wavefront''' is incident on the boundary.
  
 
|-
 
|-
Line 416: Line 413:
 
|| Observe the pink points on the boundary between the media.
 
|| Observe the pink points on the boundary between the media.
  
−
Each pink point is the source of spherical wavefront.
+
Each pink point is the source of '''spherical wavefront'''.
  
 
|-
 
|-
Line 427: Line 424:
  
 
|-
 
|-
−
||  
+
|| Cursor on the interface.
 
|| Note that the waves in '''Medium 2''' move with less velocity as compared to '''Medium 1'''.
 
|| Note that the waves in '''Medium 2''' move with less velocity as compared to '''Medium 1'''.
  
−
This is because, the medium 2 has higher refractive index.
+
This is because, the '''medium 2''' has higher refractive index.
  
 
So here the waves move with less velocity.
 
So here the waves move with less velocity.
Line 444: Line 441:
 
|-
 
|-
 
|| Point to the line drawn.
 
|| Point to the line drawn.
−
|| Observe the tangent drawn to all these spherical waves.
+
|| Observe the tangent drawn to all these '''spherical waves'''.
  
−
This line, here is the source for the secondary wavefront.
+
This line, here is the source of the secondary '''wavefront'''.
  
 
|-
 
|-
 
|| Points on the wavelets.
 
|| Points on the wavelets.
−
|| So, the points on every wavelet result in the formation of secondary wavefront.
+
|| So, the points on every wavelet results in the formation of secondary '''wavefront'''.
  
 
|-
 
|-
−
||  
+
|| Point to the values.
 
|| Here the values of '''Angle of incidence''', '''reflection '''and '''refraction '''are given.
 
|| Here the values of '''Angle of incidence''', '''reflection '''and '''refraction '''are given.
  
Line 462: Line 459:
 
|-
 
|-
 
|| Point and show the direction of propagation of the red and blue waves.
 
|| Point and show the direction of propagation of the red and blue waves.
−
|| Direction of propogation changes when waves move from medium 1 to medium 2.  
+
|| Direction of propagation changes when waves move from '''medium 1''' to '''medium 2'''.  
  
 
|-
 
|-
−
|| Again click on the '''Next step''' button.
+
|| Click on the '''Next step''' button.
 
|| Again click on the '''Next step''' button.
 
|| Again click on the '''Next step''' button.
  
Line 478: Line 475:
 
|-
 
|-
 
|| Point and show the perpendicular lines.
 
|| Point and show the perpendicular lines.
−
|| Observe that these lines of propagation are perpendicular to the wavefronts.
+
|| Observe that these lines of propagation are perpendicular to the '''wavefronts'''.
  
 
|-
 
|-
Line 486: Line 483:
 
|-
 
|-
 
|| Change '''Angle of incidence '''<nowiki>= 60 degrees.</nowiki>
 
|| Change '''Angle of incidence '''<nowiki>= 60 degrees.</nowiki>
−
|| Change the '''Angle of incidence '''to 60 degrees.
+
|| Change the '''Angle of incidence''' to 60 degrees.
  
 
|-
 
|-
 
|| Click on the '''Next step'''.
 
|| Click on the '''Next step'''.
−
|| Click on the '''Next step '''button.
+
|| Click on the '''Next step''' button.
  
 
|-
 
|-
 
|| Point the series of waves.
 
|| Point the series of waves.
−
|| Here we can see a series of wavefronts that are incident on boundary surface.
+
|| Here we can see a series of '''wavefronts''' that are incident on the boundary surface.
  
 
|-
 
|-
 
|| Cursor on both mediums.
 
|| Cursor on both mediums.
−
|| Observe the speed and wavelength of wavefronts in both the media.
+
|| Observe the speed and wavelength of '''wavefronts''' in both the media.
  
 
|-
 
|-
 
|| Point to the denser medium.
 
|| Point to the denser medium.
−
|| The wavelength and speed of the wavefront decreases in the denser medium.
+
|| The wavelength and speed of the '''wavefront''' decreases in the denser medium.
  
−
But the frequency of the plane wavefronts remains the same.
+
But the frequency of the plane '''wavefronts''' remains the same.
  
 
|-
 
|-
 
|| make the refractive index of 1 to 2 and refractive index of 2 to 1.
 
|| make the refractive index of 1 to 2 and refractive index of 2 to 1.
−
|| Let us reverse the refractive indices and observe the formation of wavefronts.
+
|| Let us reverse the refractive indices and observe the formation of '''wavefronts'''.
  
 
|-
 
|-
−
|| Point to the wavefronts.
+
|| Point to the '''wavefronts'''.
−
|| Here the speed of the wavefront decreases, as it moves from denser medium.
+
|| Here the speed of the '''wavefront''' decreases, as it moves from denser medium.
  
 
|-
 
|-
Line 520: Line 517:
 
|| This shows the total internal reflection.  
 
|| This shows the total internal reflection.  
  
−
Here the incident wavefront is completely reflected and not refracted.
+
Here the incident '''wavefront''' is completely reflected and not refracted.
  
−
This results in the formation of critical angle.
+
This results in the formation of '''critical angle'''.
  
 
|-
 
|-
Line 529: Line 526:
 
'''Assignment'''
 
'''Assignment'''
  
−
Change the refractive index values of both media as given in the previous '''App'''.
+
Change the refractive index values of both media as given in Refraction of Light '''App'''.
  
−
Observe the formation of wavefront and give an explanation.
+
Observe the formation of '''wavefront''' and give an explanation.
  
 
|| As an assignment
 
|| As an assignment
  
−
Change the refractive index values of both media as given in the previous '''App'''.
+
Change the refractive index values of both media as given in Refraction of Light '''App'''.
  
−
Observe the formation of wavefront and give an explanation.
+
Observe the formation of '''wavefront''' and give an explanation.
  
 
|-
 
|-
Line 549: Line 546:
 
|| Using these '''Apps''', we have
 
|| Using these '''Apps''', we have
  
−
Simulated reflection and refraction of a light ray.
+
'''Simulated''' reflection and refraction of a light ray.
  
 
Calculated the angles of reflection and refraction.
 
Calculated the angles of reflection and refraction.
  
−
Changed the medium and angle of incidence to verify '''Snell's Law'''.
+
Changed the medium and '''angle of incidence''' to verify '''Snell's Law'''.
  
 
|-
 
|-
Line 559: Line 556:
  
 
'''Summary'''  
 
'''Summary'''  
−
|| Calculated the value of critical angle.
+
|| Calculated the value of '''critical angle'''.
  
 
Verified '''Huygens' principle'''.
 
Verified '''Huygens' principle'''.
−
 
  
 
|-
 
|-
Line 569: Line 565:
 
'''Acknowledgement'''
 
'''Acknowledgement'''
  
−
These Apps are created by Walter-fendt and his team.
+
These '''Apps''' are created by Walter-fendt and his team.
 
|| These '''Apps''' were created by Walter-fendt and his team.
 
|| These '''Apps''' were created by Walter-fendt and his team.
  
Line 576: Line 572:
  
 
'''About the Spoken Tutorial project.'''
 
'''About the Spoken Tutorial project.'''
−
 
−
 
  
 
|| The video at the following link summarizes the Spoken Tutorial project.
 
|| The video at the following link summarizes the Spoken Tutorial project.
Line 588: Line 582:
 
'''Spoken Tutorial workshops.'''
 
'''Spoken Tutorial workshops.'''
  
−
|| The&nbsp;'''Spoken Tutorial Project&nbsp;'''team,
+
|| The '''Spoken Tutorial Project'''team,
  
 
conducts workshops and gives certificates.
 
conducts workshops and gives certificates.
Line 619: Line 613:
 
||  
 
||  
 
|| This is Himanshi Karwanje from IIT Bombay  
 
|| This is Himanshi Karwanje from IIT Bombay  
−
 
  
 
Thank you for joining.
 
Thank you for joining.
−
 
−
 
  
 
|-
 
|-
 
|}
 
|}

Latest revision as of 18:21, 31 July 2020

Visual Cue Narration
Slide Number 1

Title slide

Welcome to the Spoken Tutorial on Reflection and Refraction.
Slide Number 2

Learning Objectives

In this tutorial, we will learn to,

Simulate reflection and refraction of a light ray.

Calculate the angles of reflection and refraction.

Change the medium and angle of incidence to verify Snell's Law.

Slide Number 3

Learning Objectives

Calculate the value of critical angle.

Verify Huygens' principle.

Slide Number 4

System Requirements

Here I am using,

Ubuntu Linux OS version 16.04

Firefox web browser version 62.0.3

Slide Number 5

Pre-requisites

https://spoken-tutorial.org/

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

For pre-requisites tutorials please visit this site.

Slide Number 6

Link for Apps on physics.

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

Use the given link to download the Apps.
Open the Downloads folder. I have already downloaded the Apps on Physics to my Downloads folder.


Slide Number 7

Apps on Physics

In this tutorial, we will use,

Refraction of Light and

Reflection and Refraction of Light Waves Apps.


Right-click on refraction_en.htm file.

Select the option Open With Firefox web Browser option.

Cursor on the App.

Right-click on refraction_en.htm file.

Select the option Open With Firefox web Browser.

Reflection and Refraction of Light App opens in the browser.

Cursor on the interface. The App shows reflection and refraction of light through a given medium.
Point to air and water on the interface The default media are air and water.
Point to air.

Point to water.

Note that the medium with lesser refractive index is shown in white background.

The medium with greater refractive index is shown in blue background.

Point to the light that has been incident. Light from the top left corner, strikes the boundary surface of the two media.
Point to both reflection and refraction angles. It shows reflection and refraction.
Point to blue angles. Reflection is shown by the blue coloured angle.
Point to black and blue angles. Observe that the angle of incidence and reflection are the same.
Point to the refraction. Here we see the refraction of light.
Show the phenomena with the motion of the cursor. When light travels from rarer medium to denser medium, it bends towards normal.
Cursor on the green panel. On the green panel we have a choice to change a few parameters.
Point to the drop downs. Let us reverse the two media using the drop downs.
Click on the first drop down and change the medium to water. Select water as the upper medium.
Click on second drop down.

Select air from the drop down.

Select air as the lower medium.
Move the cursor to show the movements Here the ray of light travels from denser to rarer medium.

The ray bends away from the normal.

Click on both drop down to show the material medium. Note that both the drop downs show the same material media.
Point to each drop down. Below the drop down, we see two text fields.

These are provided to enter the values of refractive indices.

Enter the value 4 in the 1st index of refraction and show the change. Here we can also change the values manually between the range of 1 to 5.
Click on F5 key on the keyboard. Press F5 key on the keyboard to refresh the App.
Change the values from 0.1 degrees to 90 degrees and show the changes.

Click on F5 key on the keyboard to refresh and show the default value.

Next Angle of incidence can be changed from 0.1 degrees to 90 degrees.

Press F5 key to see the default value.

It shows 30 degrees.

Point below the text fields. Below the text fields App shows the Angle of reflection and refraction.
Point to the graph. Graph shows the angle of refraction with angle of incidence.
Click and drag the angle of incidence.

Drag it slowly.

We can also change the angle of incidence by dragging this red coloured ray.
Point and show the changes when the angle of incidence is changed. Notice the change in angle of reflection and refraction.

Simultaneously observe the graph.

Cursor on the interface. Now from the graph we will learn the two cases of Snell’s law.
Slide Number 8

Snell’s Law of Refraction

sin i / sin r = n21

“n21” is the refractive index of the second medium w.r.t first.

Before that let us state Snell’s law of refraction.

Ratio of sine of angle of incidence to sine of angle of refraction is a constant.

n21 is the refractive index of second medium with respect to first medium.

Slide Number 9

Snell’s Law of Refraction

Case1: If n21 > 1, angle of refraction is less than angle of incidence.

Case2: If n21 < 1, angle of refraction is greater than angle of incidence.

Here are the 2 cases of Snell’s law.

1. If n21 is greater than 1, angle of refraction is less than angle of incidence.

2. If n21 is less than 1, angle of refraction is greater than angle of incidence.

Edit the value of Angle of incidence to 20 degrees. Change the Angle of incidence to 20 degrees.

Observe that the angle of refraction has changed to 14.9.

Point to the graph and values of the angles. This graph shows the first case of Snell’s law.

Here angle of incidence is greater than the

angle of refraction.

Point to the value of refractive index of the second medium. Observe that the light ray bends towards the normal.
Cursor on the interface. Let us see what happens, when incident ray passes from denser to rarer medium.
Click on the first drop down and change the medium to diamond. From the first drop down change the material medium to diamond.
Point to show the refraction. Notice that the light ray has bent away from the normal.
Point to the graph. This graph shows the second case of Snell’s law.
Point to show Angle of refraction. Here the angle of refraction is greater than the angle of incidence.
Change the Angle of incidence to 30 degrees. Increase the Angle of incidence to 30 degrees.
Point to the refracted ray. The refracted ray has bent still more further away from the normal.
Change the Angle of incidence to 35 degrees. Again increase the angle of incidence to 35 degrees.

In this case observe that the refraction is not possible.

Point to the reflected ray. Here the incident ray is totally reflected.
Cursor on the interface. This phenomenon is known as total internal reflection.

Here the critical angle is formed.

Point to the Critical angle. The critical angle for diamond and water is 33.3 degrees.
Slide Number 10

Critical angle

ic= sin-1(n2/n1)

ic= Critical angle

n1= Refractive index of first medium

n2= Refractive index of the second medium

Now we will calculate the critical angle using the formula.
Slide Number 11

Tabular column

Let us make a tabular column to calculate critical angle for two different media.
point to the calculated values. Here I have calculated the critical angle for diamond and water.
Point to the on the interface Critical angle. The calculated value is comparable to the value shown in the App.
Slide Number 12

Tabular column

Now enter these values in the table.
Change the upper medium to water and lower medium to air. Next change the upper medium to water and lower medium to air.
Slide Number 13

Tabular Column

Show one glimpse of the table

Note the refractive indices for both the media.
Show the calculation of critical angle as image. Then calculate the critical angle using the above formula.
Point to show the values. Observe that the values are comparable.
Slide Number 14

Tabular column

Note these values in the table.
Slide Number 15

Assignment

Show the incomplete table.

As an assignment
  • Note the values of refractive indices for the following media from the App.
  • Calculate the critical angle for the two media.
  • Compare the values with the ones shown in the App.
Cursor on the interface. Now we will move on to the next App.
Right click on refractionhuygens_en.htm.

Open With Firefox Web Browser.

Right click on refractionhuygens_en.htm file.

Open With Firefox Web Browser.

The App opens in the browser.

Highlight the main topic from the screen. App shows Reflection and Refraction of light waves using Huygen's principle.
Click on the Restart button. Click on the Restart button.
Point to the wavefront. Here the plane wavefront is incident diagonally on the boundary of the media.
Click on the Next step button. Click on the Next step button.
Point to the box and scroll the slider.(Highlight the box) Explanation of each step is provided in this text box.
Point to the wavefronts. Note the change in media, when the wavefront is incident on the boundary.
Click on the Pause button. Click on the Pause button.
Point to the pink point on the boundary. Observe the pink points on the boundary between the media.

Each pink point is the source of spherical wavefront.

Point to the waves in Medium1 and Medium 2. These generating waves in the Medium 1 and Medium 2 are the wavelets.
Click on the Resume button. Click on the Resume button.
Cursor on the interface. Note that the waves in Medium 2 move with less velocity as compared to Medium 1.

This is because, the medium 2 has higher refractive index.

So here the waves move with less velocity.

Click on the Next step button. Click on the Next step button.
Click on the Pause button. Click on the Pause button.
Point to the line drawn. Observe the tangent drawn to all these spherical waves.

This line, here is the source of the secondary wavefront.

Points on the wavelets. So, the points on every wavelet results in the formation of secondary wavefront.
Point to the values. Here the values of Angle of incidence, reflection and refraction are given.
Click on the Resume button. Click on the Resume button.
Point and show the direction of propagation of the red and blue waves. Direction of propagation changes when waves move from medium 1 to medium 2.
Click on the Next step button. Again click on the Next step button.
Point to direction of the propagation of waves. Here the direction of the propagation of waves is shown.
Click on the Pause button. Click on the Pause button.
Point and show the perpendicular lines. Observe that these lines of propagation are perpendicular to the wavefronts.
Click on the Resume button. Click on the Resume button.
Change Angle of incidence = 60 degrees. Change the Angle of incidence to 60 degrees.
Click on the Next step. Click on the Next step button.
Point the series of waves. Here we can see a series of wavefronts that are incident on the boundary surface.
Cursor on both mediums. Observe the speed and wavelength of wavefronts in both the media.
Point to the denser medium. The wavelength and speed of the wavefront decreases in the denser medium.

But the frequency of the plane wavefronts remains the same.

make the refractive index of 1 to 2 and refractive index of 2 to 1. Let us reverse the refractive indices and observe the formation of wavefronts.
Point to the wavefronts. Here the speed of the wavefront decreases, as it moves from denser medium.
Cursor on the interface.

Point to show the critical angle.

This shows the total internal reflection.

Here the incident wavefront is completely reflected and not refracted.

This results in the formation of critical angle.

Slide Number 16

Assignment

Change the refractive index values of both media as given in Refraction of Light App.

Observe the formation of wavefront and give an explanation.

As an assignment

Change the refractive index values of both media as given in Refraction of Light App.

Observe the formation of wavefront and give an explanation.

Let us summarize
Slide Number 17

Summary

Using these Apps, we have

Simulated reflection and refraction of a light ray.

Calculated the angles of reflection and refraction.

Changed the medium and angle of incidence to verify Snell's Law.

Slide Number 18

Summary

Calculated the value of critical angle.

Verified Huygens' principle.

Slide Number 19

Acknowledgement

These Apps are 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

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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

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