Difference between revisions of "PhET/C2/Bending-Light/English-timed"

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(Created page with "{| border = 1 |'''Time''' |'''Narration''' |- |00:01 |Welcome to this tutorial on '''Bending Light''', an interactive PhET simulation. |- |00:07 | In this tutorial we wil...")
 
 
(4 intermediate revisions by 2 users not shown)
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|-  
 
|-  
 
|00:01
 
|00:01
−
|Welcome to this tutorial on '''Bending Light''', an interactive PhET simulation.  
+
|Welcome to this tutorial on '''Bending Light''', an interactive '''PhET simulation'''.  
  
 
|-  
 
|-  
 
|00:07
 
|00:07
−
| In this tutorial we will learn,
+
| In this tutorial, we will learn how to use''' Bending Light''', interactive '''PhET simulation'''.  
−
 
+
−
How to use''' Bending Light, '''interactive PhET simulation.  
+
  
 
|-  
 
|-  
 
|00:14
 
|00:14
−
| To follow this tutorial,  
+
| To follow this tutorial, learners should be familiar with topics in high school science.  
−
 
+
−
Learners should be familiar with topics in high school science.  
+
  
 
|-  
 
|-  
Line 23: Line 19:
 
| Here I am using -  
 
| Here I am using -  
  
−
Ubuntu Linux OS Version 14.04  
+
'''Ubuntu Linux OS''' version 14.04  
  
−
Java version 1.7.0  
+
'''Java''' version 1.7.0  
  
−
Firefox Web Browser Version 53.02.2.  
+
'''Firefox Web Browser''' version 53.02.2.  
  
 
|-  
 
|-  
 
|  00:37
 
|  00:37
−
| Using this simulation we will learn,
+
| Using this simulation, we will learn:
  
−
Reflection of light  
+
1. Reflection of light  
  
−
Refraction of light  
+
2. Refraction of light  
  
−
Dispersion of light.
+
3. Dispersion of light  
  
−
How reflection and refraction varies with different material media.  
+
4. How reflection and refraction vary with different material media.  
  
 
|-  
 
|-  
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| We will also learn to,  
 
| We will also learn to,  
  
−
Use optical instruments like prism and lens
+
1. Use optical instruments like prism and lens
  
−
Measure intensity of light
+
2. Measure intensity of light
  
 
|-  
 
|-  
 
|01:02
 
|01:02
−
| Measure velocity of light and  View different wave patterns.  
+
|3. Measure velocity of light and  view different wave patterns.  
  
 
|-  
 
|-  
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|-  
 
|-  
 
| 01:14
 
| 01:14
−
| '''Reflection''' is bouncing back of a light ray after hitting any surface.  
+
| Reflection, is bouncing back of a light ray after hitting any surface.  
  
 
For example- A mirror reflects the image of the observer.  
 
For example- A mirror reflects the image of the observer.  
Line 65: Line 61:
 
|-  
 
|-  
 
| 01:26
 
| 01:26
−
|'''Refraction''' is bending of a light ray, when it enters a medium.  
+
|Refraction, is bending of a light ray when it enters a medium.  
  
 
|-  
 
|-  
Line 71: Line 67:
 
| Light changes its speed and angle of propagation as it enters a different medium.  
 
| Light changes its speed and angle of propagation as it enters a different medium.  
  
−
For Example: Bending image of a Pencil in a beaker of water.  
+
For Example: Bending image of a pencil in a beaker of water.  
  
 
|-  
 
|-  
 
| 01:45
 
| 01:45
−
|'''Dispersion ''' is a process of splitting of white light into seven colours.  
+
|Dispersion, is a process of splitting of white light into seven colours.  
  
 
|-  
 
|-  
 
|01:51
 
|01:51
−
| For Example, Formation of a Rainbow on a cloudy day.  
+
| For Example, formation of a rainbow on a cloudy day.  
  
 
|-  
 
|-  
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|-  
 
|-  
 
| 02:03
 
| 02:03
−
|I have already downloaded '''Bending light''' simulation to my '''Downloads''' folder.  
+
|I have already downloaded '''Bending light simulation''' to my '''Downloads''' folder.  
  
 
|-  
 
|-  
 
| 02:09
 
| 02:09
−
| To open the simulation, right click on '''bending-light_en.html''' file.  
+
| To open the simulation, right-click on '''bending-light_en.html''' file.  
  
 
|-  
 
|-  
 
|02:14
 
|02:14
−
| Select '''Open With Firefox Web Browser''' option.  File opens in the browser.  
+
| Select '''Open With Firefox Web Browser''' option.   
 +
File opens in the browser.  
  
 
|-  
 
|-  
 
|02:23
 
|02:23
−
|This is the interface for '''Bending Light''' simulation.  
+
|This is the '''interface''' for '''Bending Light simulation'''.
 
|-  
 
|-  
 
|02:28
 
|02:28
−
|The interface has three screens,
+
|The interface has three screens-''' Intro, Prisms''' and  ''' More Tools'''.
−
 
+
−
''' Intro '''
+
−
 
+
−
''' Prisms''' and  ''' More Tools '''
+
  
 
|-  
 
|-  
 
|02:35
 
|02:35
−
|Let us begin our simulation with '''Intro''' screen. Click on '''Intro''' screen to open it.  
+
|Let us begin our simulation with '''Intro''' screen.  
 +
 
 +
Click on '''Intro''' screen to open it.  
  
 
|-  
 
|-  
 
| 02:42
 
| 02:42
−
| This screen has, '''Ray''' and '''Wave''' radio buttons on the top left corner.  A movable '''laser'''  pointer to turn on the '''laser'''  light.  
+
| This screen has '''Ray''' and '''Wave''' radio buttons on the top left corner,
 +
 
 +
a movable '''laser'''  pointer to turn on the '''laser'''  light.  
  
 
|-  
 
|-  
 
|02:53
 
|02:53
−
| We can see green coloured arrows, when mouse pointer is, placed on the '''laser'''. These arrows show the direction, in which the '''laser'''  moves.  
+
| We can see green colored arrows when '''mouse pointer''' is placed on the '''laser'''.  
 +
 
 +
These arrows show the direction in which the '''laser'''  moves.  
  
 
|-  
 
|-  
 
|03:06
 
|03:06
−
| Click and drag the '''laser''', to move it from zero to 90 degrees.  Let us bring the '''laser'''  to its default position.  
+
| Click and drag the '''laser'''  to move it from zero to 90 degrees.   
 +
 
 +
Let us bring the '''laser'''  to its default position.  
  
 
|-  
 
|-  
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|-  
 
|-  
 
| 03:21
 
| 03:21
−
|Here we see a tool box.  It consists of a, '''Protractor''' to measure angles '''Intensity''' tool to measure intensity of light.
+
|Here we see a tool box.   
 +
 
 +
It consists of a protractor to measure angles, '''Intensity''' tool to measure intensity of light.
  
 
|-  
 
|-  
 
|03:32
 
|03:32
−
| Below the tool box we have a check box to show '''Normal'''.  A '''Reset ''' button is provided at the right hand side corner, to reset the simulation.  
+
| Below the tool box, we have a check-box to show '''Normal'''.   
 +
 
 +
A '''Reset''' button is provided at the right hand side corner, to reset the simulation.  
  
 
|-  
 
|-  
 
| 03:44
 
| 03:44
−
| Let us begin the simulation.  
+
| Let us begin the '''simulation'''.  
  
 
|-  
 
|-  
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|-  
 
|-  
 
|03:54
 
|03:54
−
| By default '''Ray''' is selected.  To turn on the '''laser''', click the red button on the '''laser'''  pointer.  
+
| By default '''Ray''' is selected.   
 +
 
 +
To turn on the '''laser''', click the red button on the '''laser'''  pointer.  
  
 
|-  
 
|-  
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|-  
 
|-  
 
| 04:09
 
| 04:09
−
| Observe that, as we drag the '''laser'''  pointer, angle of reflection and refraction changes.  
+
| Observe that as we drag the '''laser'''  pointer, angle of reflection and refraction changes.  
  
 
|-  
 
|-  
 
| 04:17
 
| 04:17
−
|Let’s use the '''protractor''' tool to measure angle of, incidence refraction and  reflection.  
+
|Let’s use the '''protractor''' tool to measure angle of incidence refraction and  reflection.  
  
 
|-  
 
|-  
 
|04:25
 
|04:25
−
| Place the '''protractor''' at the intersection point of-
+
| Place the protractor at the intersection point of incident ray, normal, refracted and reflected rays.  
−
 
+
−
incident ray, normal, refracted and reflected rays.  
+
  
 
|-  
 
|-  
 
|04:35
 
|04:35
−
| Observe that angle of incidence is equal to angle of reflection. Drag the '''protractor''' back to its place.  
+
| Observe that angle of incidence is equal to angle of reflection.  
 +
 
 +
Drag the protractor back to its place.  
  
 
|-  
 
|-  
 
|04:44
 
|04:44
−
| Next we will move on to, right hand side of the '''Intro''' screen.  
+
| Next we will move on to right hand side of the '''Intro''' screen.  
  
 
|-  
 
|-  
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|-  
 
|-  
 
| 04:56
 
| 04:56
−
|There is a slider to change the material medium. Or buttons to click. Initially, the slider is near '''Air'''.  
+
|There is a '''slider''' to change the material medium, or buttons to click. Initially, the slider is near '''Air'''.  
  
 
|-  
 
|-  
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|-  
 
|-  
 
|05:15
 
|05:15
−
| When medium is changed the angle of refraction changes. '''Index of Refraction(n)''' also changes.  
+
| When medium is changed, the angle of refraction changes. '''Index of Refraction(n)''' also changes.  
  
 
|-  
 
|-  
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|-  
 
|-  
 
|05:32
 
|05:32
−
| By default slider is on '''Water''' in the lower medium. Drag the slider and place it between '''Water''' and '''Glass''' in the lower medium.  
+
| By default, slider is on '''Water''' in the lower medium.  
 +
 
 +
Drag the slider and place it between '''Water''' and '''Glass''' in the lower medium.  
  
 
|-  
 
|-  
 
|05:44
 
|05:44
−
|  Now lets measure, the '''intensity''' of light using '''Intensity''' tool.  
+
|  Now let's measure the intensity of light using '''Intensity''' tool.  
  
 
|-  
 
|-  
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|-  
 
|-  
 
| 06:00
 
| 06:00
−
| I will place the '''magnifier''' on the incident light. Meter shows 100% intensity.  
+
| I will place the '''magnifier''' on the incident light. '''Meter''' shows 100% intensity.  
  
 
|-  
 
|-  
 
| 06:08
 
| 06:08
−
| Now drag and place the '''magnifier''' on refracted light. Meter shows value as 86.08%. Intensity decreases because it depends on the medium.  
+
| Now, drag and place the '''magnifier''' on refracted light. '''Meter''' shows value as 86.08%.  
 +
 
 +
Intensity decreases because it depends on the medium.  
  
 
|-  
 
|-  
 
|06:24
 
|06:24
−
| As we drag the medium slider, value on the intensity meter changes. This is because angle of refraction changes.  
+
| As we drag the medium slider, value on the intensity meter changes.  
 +
 
 +
This is because angle of refraction changes.  
  
 
|-  
 
|-  
 
|06:34
 
|06:34
−
| Similarly place the '''magnifier''' on reflected light. '''Meter''' shows value as 13.55%.  
+
| Similarly, place the '''magnifier''' on reflected light. '''Meter''' shows value as 13.55%.  
  
 
|-  
 
|-  
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|-  
 
|-  
 
| 06:51
 
| 06:51
−
| Now, change '''Ray''' to '''Wave''' and observe the '''bending of light'''.  
+
| Now, change '''Ray''' to '''Wave''' and observe the bending of light.  
  
 
|-  
 
|-  
 
|  06:56
 
|  06:56
−
|Now we will move on to Prisms screen.  
+
|Now we will move on to '''Prisms''' screen.  
  
 
|-  
 
|-  
 
|  07:00
 
|  07:00
−
|Click on '''Prisms''' screen, at the bottom of the interface.  
+
|Click on '''Prisms''' screen at the bottom of the interface.  
  
 
|-  
 
|-  
 
| 07:06
 
| 07:06
−
|In this screen we have the following tools-  
+
|In this screen, we have the following tools-  
  
−
Slider to change the '''environment'''
+
Slider to change the '''environment''',
  
−
'''Monochromatic ray'''
+
Monochromatic ray,
  
 
|-  
 
|-  
 
|07:15
 
|07:15
−
| '''Monochromatic beam'''  '''White light''' Slider to change '''wavelength''' of light.  
+
| Monochromatic beam, white light, slider to change wavelength of light.  
  
 
|-  
 
|-  
 
| 07:22
 
| 07:22
−
| At the bottom of the screen we have-  
+
| At the bottom of the screen, we have-  
  
−
''' Prisms''' and '''lenses'''
+
prisms and lenses,
  
 
|-  
 
|-  
 
| 07:29
 
| 07:29
−
|Slider to change the '''Objects'''.
+
|slider to change the '''Objects''',
  
−
Check boxes for '''Reflections''', '''Normal''' and '''Protractor'''.  
+
check boxes for '''Reflections, Normal''' and '''Protractor'''.  
  
 
'''Reset''' button is at the right hand-side bottom corner.  
 
'''Reset''' button is at the right hand-side bottom corner.  
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|-  
 
|-  
 
| 07:52
 
| 07:52
−
|Here arrows indicate direction of motion. '''laser''' can be moved up and down.  
+
|Here, arrows indicate direction of motion. '''laser''' can be moved up and down.  
  
 
|-  
 
|-  
 
| 08:00
 
| 08:00
−
|Now let’s begin the simulation.  
+
|Now let’s begin the '''simulation'''.  
 
   
 
   
 
|-  
 
|-  
 
| 08:03
 
| 08:03
−
|Click on '''Monochromatic beam'''. Click on the '''laser'''  light.  
+
|Click on '''monochromatic beam'''. Click on the '''laser'''  light.  
  
 
|-  
 
|-  
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|-  
 
|-  
 
| 08:14
 
| 08:14
−
| Place a '''Prism''' in the path of light. You can see bending of light.  
+
| Place a prism in the path of light. You can see bending of light.  
  
 
|-  
 
|-  
 
|08:21
 
|08:21
−
| Move the '''wavelength''' slider gradually from red to violet. Notice the bending of light as '''wavelength''' changes.  
+
| Move the '''wavelength slider''' gradually from red to violet.  
 +
 
 +
Notice the bending of light as wavelength changes.  
  
 
|-  
 
|-  
 
| 08:32
 
| 08:32
−
|'''Prism''' is provided with a screw at its corner.  
+
|Prism is provided with a screw at its corner.  
  
 
|-  
 
|-  
 
| 08:38
 
| 08:38
−
|Drag the screw to change the direction of the '''prism'''. As we change the direction notice the bending of light.  
+
|Drag the screw to change the direction of the prism.
 +
 
 +
As we change the direction, notice the bending of light.  
  
 
|-  
 
|-  
 
| 08:47
 
| 08:47
−
|As an assignment  
+
|As an assignment, change prism to glass slabs and observe the bending of light.  
−
Change prism to glass slabs and observe the bending of light.  
+
  
 
|-  
 
|-  
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|-  
 
|-  
 
|08:59
 
|08:59
−
| Click on '''White light''' tool. Observe the dispersion of light.  
+
| Click on white light tool. Observe the dispersion of light.  
  
 
|-  
 
|-  
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|-  
 
|-  
 
|  09:11
 
|  09:11
−
|Place a lens in the path of dispersed beam of light. The dispersed beam of light shows multiple reflections.  
+
|Place a lens in the path of dispersed beam of light.  
 +
 
 +
The dispersed beam of light shows multiple reflections.  
  
 
|-  
 
|-  
 
|09:26
 
|09:26
−
| As an assignment  
+
| As an assignment:
  
 
Use various lenses and observe the dispersion.  
 
Use various lenses and observe the dispersion.  
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|-  
 
|-  
 
| 09:37
 
| 09:37
−
|Now we move on to More Tools screen.  
+
|Now we move on to '''More Tools''' screen.  
  
 
|-  
 
|-  
 
| 09:41
 
| 09:41
−
|Click on '''More Tools''' screen. '''More Tools''' screen has a combination of tools from '''Intro''' and '''Prisms''' screens.  
+
|Click on '''More Tools''' screen.  
 +
 
 +
'''More Tools''' screen has a combination of tools from '''Intro''' and '''Prisms''' screens.  
  
 
|-  
 
|-  
 
|  09:51
 
|  09:51
−
|Tool box at the bottom has two additional tools:
+
|Tool box at the bottom has two additional tools '''Speed''' and '''Time'''.
 +
 
 +
At the bottom we also have '''Angles''' check box.
  
−
'''Speed''' and '''Time'''.At the bottom we also have '''Angles''' check box. Click on the '''Angles''' check box.  
+
Click on the '''Angles''' check box.  
  
 
|-  
 
|-  
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|Now we will change the '''laser'''  light to Wave.  
 
|Now we will change the '''laser'''  light to Wave.  
  
−
Additionally radio buttons-  
+
Additionally radio buttons- '''Normal''' and '''Slow Motion'''. Also,  '''Play/Pause''' and '''Forward''' buttons appear.  
−
 
+
−
'''Normal''' and '''Slow Motion''' Also,  '''Play/Pause''' and '''Forward''' buttons appear.  
+
  
 
|-  
 
|-  
 
|  10:18
 
|  10:18
−
|let’s begin the simulation  
+
|Let’s begin the '''simulation'''.
  
 
|-  
 
|-  
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|-  
 
|-  
 
|10:23
 
|10:23
−
|Click on red button to turn on the '''laser'''  pointer.  let’s use the '''Time''' tool.  
+
|Click on red button to turn on the '''laser'''  pointer.  Let’s use the '''Time''' tool.  
  
 
|-  
 
|-  
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|-  
 
|-  
 
|10:39
 
|10:39
−
| Place one of the '''magnifiers''' on incident wave and observe the wave pattern. Now place the other '''magnifier''' on the refracted wave.  
+
| Place one of the '''magnifiers''' on incident wave and observe the wave pattern.  
 +
 
 +
Now place the other '''magnifier''' on the refracted wave.  
  
 
|-  
 
|-  
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|-  
 
|-  
 
|10:56
 
|10:56
−
| Place the '''magnifier''' on the reflected wave. Observe that, the new wave pattern is with reduced '''amplitude'''.  
+
| Place the '''magnifier''' on the reflected wave.  
 +
 
 +
Observe that the new wave pattern is with reduced amplitude.  
  
 
|-  
 
|-  
 
|11:06
 
|11:06
−
|This is because, the reflected wave has much lower '''intensity'''.  
+
|This is because, the reflected wave has much lower intensity.  
  
 
|-  
 
|-  
 
|11:12
 
|11:12
−
| Drag and place the '''Speed''' tool on the refracted wave. The speed is 0.67 c. Here c is velocity of light equal to 3x10^8 m/s. Value of speed decreases,
+
| Drag and place the '''Speed''' tool on the refracted wave.  
 +
 
 +
The speed is 0.67 c. Here '''c''' is velocity of light equal to 3x10^8 m/s. Value of speed decreases.
  
 
|-  
 
|-  
 
|11:33
 
|11:33
−
|This is because velocity of light decreases in a material medium.  
+
|This is because, velocity of light decreases in a material medium.  
  
 
|-  
 
|-  
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|-  
 
|-  
 
| 11:48
 
| 11:48
−
| In this tutorial we have learnt,
+
| In this tutorial, we have learnt how to use '''Bending Light''', interactive '''PhET simulation'''.  
−
 
+
−
How to use '''Bending Light''', interactive PhET simulation.  
+
  
 
|-  
 
|-  
 
|11:57
 
|11:57
−
| Using this simulation we have learnt,
+
| Using this '''simulation''', we have learnt:
  
−
Reflection of light  
+
1. Reflection of light  
  
−
Refraction of light  
+
2. Refraction of light  
  
−
Dispersion of light  
+
3. Dispersion of light  
  
−
How reflection and refraction varies with different material media.
+
4. How reflection and refraction varies with different material media.
  
 
|-  
 
|-  
 
|12:12
 
|12:12
−
|We have also learnt to,
+
|We have also learnt to:
  
−
Use optical instruments like prism and lens  
+
1. Use optical instruments like prism and lens  
  
 
|-  
 
|-  
 
|12:19
 
|12:19
−
|Measure intensity of light Measure velocity of light and View different wave patterns.  
+
|2. Measure intensity of light, measure velocity of light and view different wave patterns.  
  
 
|-  
 
|-  
 
|12:29
 
|12:29
−
| The video at the following link summarizes the Spoken Tutorial project. Please download and watch it.  
+
| The video at the following link summarizes the '''Spoken Tutorial''' project. Please download and watch it.  
  
 
|-  
 
|-  
 
| 12:36
 
| 12:36
−
|The '''Spoken Tutorial Project '''team,conducts workshops using spoken tutorials and gives certificates on passing online tests.
+
|The '''Spoken Tutorial''' Project team conducts workshops using spoken tutorials and gives certificates on passing online tests.
 
   
 
   
 
|-
 
|-
Line 450: Line 474:
 
|-  
 
|-  
 
| 12:54
 
| 12:54
−
|This project is partially funded by, Pandit Madan Mohan Malaviya National Mission on Teachers and Teaching.  
+
|This project is partially funded by Pandit Madan Mohan Malaviya National Mission on Teachers and Teaching.  
  
 
|-  
 
|-  
 
| 13:03
 
| 13:03
−
| Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India. More information on this mission is available at this link.  
+
| Spoken Tutorial Project is funded by '''NMEICT, MHRD,''' Government of India. More information on this mission is available at this link.  
  
 
|-  
 
|-  
 
|  13:17
 
|  13:17
−
| This is Madhuri Ganapathi from IIT-Bombay signing off. Thank you for joining  
+
| This is Madhuri Ganapathi from IIT-Bombay, signing off. Thank you for joining  
−
 
+
|-
 
|}
 
|}

Latest revision as of 17:41, 10 August 2018

Time Narration
00:01 Welcome to this tutorial on Bending Light, an interactive PhET simulation.
00:07 In this tutorial, we will learn how to use Bending Light, interactive PhET simulation.
00:14 To follow this tutorial, learners should be familiar with topics in high school science.
00:21 Here I am using -

Ubuntu Linux OS version 14.04

Java version 1.7.0

Firefox Web Browser version 53.02.2.

00:37 Using this simulation, we will learn:

1. Reflection of light

2. Refraction of light

3. Dispersion of light

4. How reflection and refraction vary with different material media.

00:52 We will also learn to,

1. Use optical instruments like prism and lens

2. Measure intensity of light

01:02 3. Measure velocity of light and view different wave patterns.
01:08 Let’s define reflection, refraction and dispersion.
01:14 Reflection, is bouncing back of a light ray after hitting any surface.

For example- A mirror reflects the image of the observer.

01:26 Refraction, is bending of a light ray when it enters a medium.
01:32 Light changes its speed and angle of propagation as it enters a different medium.

For Example: Bending image of a pencil in a beaker of water.

01:45 Dispersion, is a process of splitting of white light into seven colours.
01:51 For Example, formation of a rainbow on a cloudy day.
01:57 So, let's begin.
01:59 Use the given link to download the simulation.

http://phet.colorado.edu

02:03 I have already downloaded Bending light simulation to my Downloads folder.
02:09 To open the simulation, right-click on bending-light_en.html file.
02:14 Select Open With Firefox Web Browser option.

File opens in the browser.

02:23 This is the interface for Bending Light simulation.
02:28 The interface has three screens- Intro, Prisms and More Tools.
02:35 Let us begin our simulation with Intro screen.

Click on Intro screen to open it.

02:42 This screen has Ray and Wave radio buttons on the top left corner,

a movable laser pointer to turn on the laser light.

02:53 We can see green colored arrows when mouse pointer is placed on the laser.

These arrows show the direction in which the laser moves.

03:06 Click and drag the laser to move it from zero to 90 degrees.

Let us bring the laser to its default position.

03:16 Now let’s move onto the tools at the bottom left.
03:21 Here we see a tool box.

It consists of a protractor to measure angles, Intensity tool to measure intensity of light.

03:32 Below the tool box, we have a check-box to show Normal.

A Reset button is provided at the right hand side corner, to reset the simulation.

03:44 Let us begin the simulation.
03:47 We can focus light in the form of a Ray , or a Wave depending on what we choose.
03:54 By default Ray is selected.

To turn on the laser, click the red button on the laser pointer.

04:03 Notice that laser light gets reflected and refracted.
04:09 Observe that as we drag the laser pointer, angle of reflection and refraction changes.
04:17 Let’s use the protractor tool to measure angle of incidence refraction and reflection.
04:25 Place the protractor at the intersection point of incident ray, normal, refracted and reflected rays.
04:35 Observe that angle of incidence is equal to angle of reflection.

Drag the protractor back to its place.

04:44 Next we will move on to right hand side of the Intro screen.
04:50 Here, we have controls to measure refractive index in both the media.
04:56 There is a slider to change the material medium, or buttons to click. Initially, the slider is near Air.
05:07 As we drag the slider, medium changes from Air to Water and then to Glass.
05:15 When medium is changed, the angle of refraction changes. Index of Refraction(n) also changes.
05:24 We can see the changing value in the box. Drag the slider back to Air in the upper medium.
05:32 By default, slider is on Water in the lower medium.

Drag the slider and place it between Water and Glass in the lower medium.

05:44 Now let's measure the intensity of light using Intensity tool.
05:49 Click and drag the Intensity tool to the medium.
05:53 Intensity tool consists of a magnifier and a meter to measure intensity of light.
06:00 I will place the magnifier on the incident light. Meter shows 100% intensity.
06:08 Now, drag and place the magnifier on refracted light. Meter shows value as 86.08%.

Intensity decreases because it depends on the medium.

06:24 As we drag the medium slider, value on the intensity meter changes.

This is because angle of refraction changes.

06:34 Similarly, place the magnifier on reflected light. Meter shows value as 13.55%.
06:44 You can drag the slider to see a different value of intensity.
06:51 Now, change Ray to Wave and observe the bending of light.
06:56 Now we will move on to Prisms screen.
07:00 Click on Prisms screen at the bottom of the interface.
07:06 In this screen, we have the following tools-

Slider to change the environment,

Monochromatic ray,

07:15 Monochromatic beam, white light, slider to change wavelength of light.
07:22 At the bottom of the screen, we have-

prisms and lenses,

07:29 slider to change the Objects,

check boxes for Reflections, Normal and Protractor.

Reset button is at the right hand-side bottom corner.

07:43 laser has a screw provided at its end. Direction of laser can be changed using this screw.
07:52 Here, arrows indicate direction of motion. laser can be moved up and down.
08:00 Now let’s begin the simulation.
08:03 Click on monochromatic beam. Click on the laser light.
08:09 Click on Reflections check box to see multiple reflections.
08:14 Place a prism in the path of light. You can see bending of light.
08:21 Move the wavelength slider gradually from red to violet.

Notice the bending of light as wavelength changes.

08:32 Prism is provided with a screw at its corner.
08:38 Drag the screw to change the direction of the prism.

As we change the direction, notice the bending of light.

08:47 As an assignment, change prism to glass slabs and observe the bending of light.
08:54 Now will see dispersion of light using white light.
08:59 Click on white light tool. Observe the dispersion of light.
09:05 Drag the Objects medium slider and observe the dispersion of light.
09:11 Place a lens in the path of dispersed beam of light.

The dispersed beam of light shows multiple reflections.

09:26 As an assignment:

Use various lenses and observe the dispersion.

09:32 Change various Environments and observe the dispersion.
09:37 Now we move on to More Tools screen.
09:41 Click on More Tools screen.

More Tools screen has a combination of tools from Intro and Prisms screens.

09:51 Tool box at the bottom has two additional tools Speed and Time.

At the bottom we also have Angles check box.

Click on the Angles check box.

10:04 Now we will change the laser light to Wave.

Additionally radio buttons- Normal and Slow Motion. Also, Play/Pause and Forward buttons appear.

10:18 Let’s begin the simulation.
10:21 Turn on the laser light.
10:23 Click on red button to turn on the laser pointer. Let’s use the Time tool.
10:31 Drag and place the Time tool in the medium. Time tool has two magnifiers and a Meter.
10:39 Place one of the magnifiers on incident wave and observe the wave pattern.

Now place the other magnifier on the refracted wave.

10:51 Observe the wave pattern. It shows a phase shift.
10:56 Place the magnifier on the reflected wave.

Observe that the new wave pattern is with reduced amplitude.

11:06 This is because, the reflected wave has much lower intensity.
11:12 Drag and place the Speed tool on the refracted wave.

The speed is 0.67 c. Here c is velocity of light equal to 3x10^8 m/s. Value of speed decreases.

11:33 This is because, velocity of light decreases in a material medium.
11:39 As an assignment,

Change material medium and notice the change in speed and wave pattern.

11:48 In this tutorial, we have learnt how to use Bending Light, interactive PhET simulation.
11:57 Using this simulation, we have learnt:

1. Reflection of light

2. Refraction of light

3. Dispersion of light

4. How reflection and refraction varies with different material media.

12:12 We have also learnt to:

1. Use optical instruments like prism and lens

12:19 2. Measure intensity of light, measure velocity of light and view different wave patterns.
12:29 The video at the following link summarizes the Spoken Tutorial project. Please download and watch it.
12:36 The Spoken Tutorial Project team conducts workshops using spoken tutorials and gives certificates on passing online tests.
12:46 For more details, please write to us. Please post your timed queries on this forum.
12:54 This project is partially funded by Pandit Madan Mohan Malaviya National Mission on Teachers and Teaching.
13:03 Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India. More information on this mission is available at this link.
13:17 This is Madhuri Ganapathi from IIT-Bombay, signing off. Thank you for joining

Contributors and Content Editors

Madhurig, PoojaMoolya, Sandhya.np14

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