PoojaMoolya: Created page with "{|border=1 |- || '''Time''' || '''Narration''' |- || 00:01 || Welcome to the Spoken Tutorial on '''Reflection and Refraction'''. |- || 00:06 || In this tutorial, we will lea..."

2020-09-15T05:19:37Z

Created page with "{|border=1 |- || '''Time''' || '''Narration''' |- || 00:01 || Welcome to the Spoken Tutorial on '''Reflection and Refraction'''. |- || 00:06 || In this tutorial, we will lea..."

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{|border=1
|-
|| '''Time'''
|| '''Narration'''

|-
|| 00:01
|| Welcome to the Spoken Tutorial on '''Reflection and Refraction'''.

|-
|| 00:06
|| In this tutorial, we will learn to,

'''Simulate''' reflection and refraction of a light ray.

|-
|| 00:13
|| Calculate the angles of reflection and refraction.

|-
|| 00:17
|| Change the medium and '''angle of incidence''' to verify '''Snell's Law'''.

|-
|| 00:22
|| Calculate the value of '''critical angle'''.

|-
|| 00:26
|| Verify '''Huygens' principle'''.

|-
|| 00:29
|| Here I am using,

Ubuntu Linux OS version 16.04

|-
|| 00:35
|| Firefox web browser version 62.0.3
|-
|| 00:41
|| To follow this tutorial, learner should be familiar with '''Apps on Physics'''.

|-
|| 00:47
|| For pre-requisites tutorials please visit this site.

|-
|| 00:52
|| Use the given link to download the '''Apps'''.

|-
|| 00:56
|| I have already downloaded the '''Apps on Physics''' to my '''Downloads''' folder.

|-
|| 01:01
|| In this tutorial, we will use,

'''Refraction of Light ''' and '''Reflection and Refraction of Light Waves Apps'''.

|-
|| 01:11
|| Right-click on '''refraction_en.htm file'''.

|-
|| 01:16
|| Select the option '''Open With Firefox web Browser.'''

|-
|| 01:21
|| '''Reflection and Refraction of Light App''' opens in the browser.

|-
|| 01:26
|| The '''App''' shows reflection and refraction of light through a given medium.

|-
|| 01:31
|| The default media are air and water.

|-
||01:36
|| Note that the medium with lesser refractive index is shown in white background.

|-
|| 01:42
|| The medium with greater refractive index is shown in blue background.

|-
|| 01:47
|| Light from the top left corner, strikes the boundary surface of the two media.

|-
|| 01:52
|| It shows reflection and refraction.

|-
|| 01:56
|| Reflection is shown by the blue coloured angle.

|-
|| 02:01
|| Observe that the angle of '''incidence''' and reflection are the same.

|-
|| 02:06
|| Here we see the refraction of light.

|-
|| 02:09
|| When light travels from rarer medium to denser medium, it bends towards '''normal'''.

|-
|| 02:16
|| On the green '''panel''' we have a choice to change a few parameters.

|-
|| 02:21
|| Let us reverse the two media using the drop downs.

|-
|| 02:26
|| Select '''water''' as the upper medium.

|-
|| 02:29
|| Select '''air''' as the lower medium.

|-
|| 02:33
|| Here the ray of light travels from denser to rarer medium.

|-
|| 02:38
|| The ray bends away from the '''normal'''.

|-
|| 02:42
|| Note that both the drop downs show the same material media.

|-
|| 02:48
|| Below the drop down, we see two text fields.

These are provided to enter the values of refractive indices.

|-
||02:48
|| Here we can also change the values manually between the range of 1 to 5.

|-
|| 03:05
|| Press '''F5''' key on the keyboard to '''refresh''' the '''App'''.

|-
|| 03:10
|| Next '''Angle of incidence''' can be changed from 0.1 degrees to 90 degrees.

|-
|| 03:18
|| Press '''F5''' key to see the default value.

It shows 30 degrees.

|-
|| 03:25
|| Below the text fields '''App''' shows the '''Angle of reflection''' and '''refraction'''.

|-
|| 03:31
|| Graph shows the angle of refraction with '''angle of incidence'''.

|-
|| 03:36
|| We can also change the '''angle of incidence''' by dragging this red coloured ray.

|-
|| 03:42
|| Notice the change in angle of reflection and refraction.

|-
|| 03:48
|| Simultaneously observe the graph.

|-
|| 03:51
|| Now from the graph we will learn the two cases of '''Snell’s law'''.

|-
|| 03:57
|| Before that let us state '''Snell’s law''' of refraction.

|-
|| 04:02
|| Ratio of '''sine''' of angle of '''incidence''' to '''sine''' of angle of '''refraction''' is a constant.

|-
|| 04:09
|| n21 is the refractive index of second medium with respect to first medium.

|-
|| 04:16
|| Here are the 2 cases of '''Snell’s law'''.

|-
|| 04:19
|| If n21 is greater than 1, angle of refraction is less than angle of '''incidence'''.

|-
|| 04:26
|| If n21 is less than 1, angle of refraction is greater than angle of '''incidence'''.

|-
|| 04:34
|| Change the '''Angle of incidence''' to 20 degrees.

|-
|| 04:38
|| Observe that the '''angle of refraction''' has changed to 14.9.

|-
|| 04:44
|| This graph shows the first case of '''Snell’s law'''.

|-
|| 04:48
|| Here angle of '''incidence''' is greater than the angle of refraction.

|-
|| 04:53
|| Observe that the light ray bends towards the '''normal'''.

|-
|| 04:58
|| Let us see what happens, when incident ray passes from denser to rarer medium.

|-
|| 05:04
|| From the first drop down change the material medium to '''diamond'''.

|-
|| 05:09
|| Notice that the light ray has bent away from the '''normal'''.

|-
|| 05:14
|| This graph shows the second case of '''Snell’s law'''.

|-
|| 05:18
|| Here the angle of refraction is greater than the angle of '''incidence'''.

|-
|| 05:23
|| Increase the '''Angle of incidence''' to 30 degrees.

|-
|| 05:27

|| The refracted ray has bent still more further away from the '''normal'''.

|-
|| 05:32
|| Again increase the '''angle of incidence''' to 35 degrees.

|-
|| 05:37
|| In this case observe that the refraction is not possible.

|-
|| 05:42
|| Here the incident ray is totally reflected.

|-
|| 05:46
|| This phenomenon is known as '''total internal reflection'''.

|-
|| 05:51
|| Here the '''critical angle''' is formed.

|-
|| 05:55
|| The '''critical angle''' for diamond and water is 33.3 degrees.

|-
|| 06:01
|| Now we will calculate the '''critical angle''' using the formula.

|-
|| 06:06
|| Let us make a tabular column to calculate '''critical angle''' for two different media.

|-
||06:13
|| Here I have calculated the '''critical angle''' for diamond and water.

|-
|| 06:18
|| The calculated value is comparable to the value shown in the '''App'''.

|-
|| 06:24
|| Now enter these values in the table.

|-
|| 06:28
|| Next change the upper medium to '''water''' and lower medium to '''air'''.

|-
|| 06:34
|| Note the refractive indices for both the media.

|-
|| 06:39
|| Then calculate the '''critical angle''' using the above formula.

|-
||06:44
|| Observe that the values are comparable.

|-
|| 06:48
|| Note these values in the table.

|-
|| 06:52
|| As an assignment

Note the values of refractive indices for the following media from the '''App'''.

|-
|| 07:00
|| Calculate the '''critical angle''' for the two media.

Compare the values with the ones shown in the '''App'''.

|-
||07:09
|| Now we will move on to the next '''App'''.

|-
|| 07:12
|| Right click on '''refractionhuygens_en.htm '''file.

|-
|| 07:18
|| '''Open With Firefox Web Browser'''.

|-
|| 07:22
|| The '''App''' opens in the browser.

|-
|| 07:25
|| '''App''' shows '''Reflection''' and '''Refraction''' of light waves using '''Huygen's''' principle.

|-
|| 07:31
|| Click on the '''Restart''' button.

|-
|| 07:34
|| Here the '''plane wavefront''' is incident diagonally on the boundary of the media.

|-
|| 07:40
|| Click on the '''Next step''' button.

|-
|| 07:44
|| Explanation of each step is provided in this text box.

|-
|| 07:49
|| Note the change in media, when the '''wavefront''' is incident on the boundary.

|-
|| 07:55
|| Click on the '''Pause''' button.

|-
|| 07:58
|| Observe the pink points on the boundary between the media.

|-
|| 08:03
|| Each pink point is the source of '''spherical wavefront'''.

|-
|| 08:08
|| These generating waves in the '''Medium 1 '''and''' Medium 2''' are the wavelets.

|-
|| 08:14
|| Click on the''' Resume''' button.

|-
|| 08:17
|| Note that the waves in '''Medium 2''' move with less velocity as compared to '''Medium 1'''.

|-
|| 08:25
|| This is because, the '''medium 2''' has higher refractive index.

So here the waves move with less velocity.

|-
|| 08:35
|| Click on the '''Next step''' button.

|-
|| 08:39
|| Click on the '''Pause''' button.

|-
|| 08:42
|| Observe the tangent drawn to all these '''spherical waves'''.

|-
|| 08:47
|| This line, here is the source of the secondary '''wavefront'''.

|-
|| 08:52
|| So, the points on every wavelet results in the formation of secondary '''wavefront'''.

|-
|| 08:59
|| Here the values of '''Angle of incidence''', '''reflection '''and '''refraction '''are given.

|-
|| 09:06
|| Click on the '''Resume''' button.

|-
|| 09:09
|| Direction of propagation changes when waves move from '''medium 1''' to '''medium 2'''.

|-
||09:16
|| Again click on the '''Next step''' button.

|-
|| 09:20
|| Here the direction of the propagation of waves is shown.

|-
|| 09:25
|| Click on the '''Pause''' button.

|-
|| 09:28
|| Observe that these lines of propagation are perpendicular to the '''wavefronts'''.

|-
|| 09:35
|| Click on the '''Resume''' button.

|-
|| 09:38
|| Change the '''Angle of incidence''' to 60 degrees.

|-
|| 09:42
|| Click on the '''Next step''' button.

|-
|| 09:45
|| Here we can see a series of '''wavefronts''' that are incident on the boundary surface.

|-
|| 09:52
|| Observe the speed and wavelength of '''wavefronts''' in both the media.

|-
|| 09:58
|| The wavelength and speed of the '''wavefront''' decreases in the denser medium.

|-
|| 10:04
|| But the frequency of the plane '''wavefronts''' remains the same.

|-
|| 10:09
|| Let us reverse the refractive indices and observe the formation of '''wavefronts'''.

|-
|| 10:15
|| Here the speed of the '''wavefront''' decreases, as it moves from denser medium.

|-
|| 10:22
|| This shows the total internal reflection.

|-
|| 10:26
|| Here the incident '''wavefront''' is completely reflected and not refracted.

This results in the formation of '''critical angle'''.

|-
||10:37
|| As an assignment

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

|-
|| 10:46
|| Observe the formation of '''wavefront''' and give an explanation.

|-
|| 10:51
|| Let us summarize

|-
|| 10:53
|| Using these '''Apps''', we have '''Simulated''' reflection and refraction of a light ray.

|-
|| 11:00
|| Calculated the angles of reflection and refraction.

|-
|| 11:05
|| Changed the medium and '''angle of incidence''' to verify '''Snell's Law'''.

|-
|| 11:10
|| Calculated the value of '''critical angle'''.

Verified '''Huygens' principle'''.

|-
|| 11:18
|| These '''Apps''' were created by Walter-fendt and his team.

|-
|| 11:23
|| The video at the following link summarizes the Spoken Tutorial project.

Please download and watch it.

|-
|| 11:31
|| The '''Spoken Tutorial Project'''team, conducts workshops and gives certificates.

For more details, please write to us.

|-
|| 11:41
|| Please post your timed queries in this forum.

|-
||11:46
|| Spoken Tutorial Project is funded by MHRD Government of India.

|-
|| 11:52
|| This is Himanshi Karwanje from IIT Bombay

Thank you for joining.

|-
|}

Apps-On-Physics/C2/Reflection-and-Refraction/English-timed - Revision history

PoojaMoolya: Created page with "{|border=1 |- || '''Time''' || '''Narration''' |- || 00:01 || Welcome to the Spoken Tutorial on '''Reflection and Refraction'''. |- || 00:06 || In this tutorial, we will lea..."