PoojaMoolya: Created page with "{|border=1 |- || '''Time ''' || '''Narration''' |- || 00:01 || Welcome to the Spoken Tutorial on '''Interference and Diffraction'''. |- || 00:07 || At the end of this tutori..."

2020-09-15T05:02:36Z

Created page with "{|border=1 |- || '''Time ''' || '''Narration''' |- || 00:01 || Welcome to the Spoken Tutorial on '''Interference and Diffraction'''. |- || 00:07 || At the end of this tutori..."

New page

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

|-
|| 00:01
|| Welcome to the Spoken Tutorial on '''Interference and Diffraction'''.

|-
|| 00:07
|| At the end of this tutorial you will be able to,

|-
|| 00:11
|| Verify the relation between wavelength and relative intensity.

|-
|| 00:16
|| Find the relation between slit width, maxima and minima.

|-
|| 00:21
|| Calculate the angle for the given maxima.

|-
|| 00:24
|| Interpret diffraction intensity profile.

|-
|| 00:28
|| Verify the relation between wavelength and angle.
|-
|| 00:33
|| Here I am using,

Ubuntu Linux OS version 16.04, Firefox Web Browser version 62.0.3

|-
|| 00:46
|| To follow this tutorial,

learner should be familiar with '''Apps on Physics'''.

|-
|| 00:52
||For Pre-requisites tutorials please visit this site.

|-
||00:58
|| I have already downloaded '''Apps on Physics '''to my '''Downloads''' folder.

|-
|| 01:03
|| In this tutorial we will use,

'''Interference of Light at a Double Slit''' and '''Diffraction of Light by a Single Slit Apps'''.

|-
|| 01:13
|| Right click on''' doubleslit_en.htm '''file.

|-
|| 01:18
||Select the '''Open With Firefox web Browser '''option'''.'''

'''App''' opens in the browser.

|-
|| 01:25
|| The '''App''' shows '''Young’s double slit '''experiment for the interference pattern.

|-
|| 01:32
|| The setup includes a slit and a semicircular screen.

|-
|| 01:39
|| On the green panel we can change the wavelength of the source light.

|-
||01:44
|| Here the range of the wavelength is from 380 nanometer to 780 nanometer.

This is the range of visible spectrum.

|-
|| 01:56
|| We can also enter the value of wavelength in the text-box.

|-
|| 02:03
|| Let us see how change in wavelength changes the interference pattern.

|-
|| 02:09
|| Drag the '''Wavelength''' slider to 380 nanometer

|-
|| 02:14
|| Click on '''Intensity profile''' radio button at the bottom of the green panel.

|-
|| 02:20
|| Drag the '''Wavelength''' slider slowly towards higher wavelength.

|-
|| 02:25
||Observe the graph showing dark and bright fringes in the intensity profile.

|-
|| 02:32
|| As the wavelength increases, distance between dark and bright fringes increases.

|-
|| 02:40
||Next Drag the '''Angle''' slider here we can change the angle from 0 degrees to 90 degrees.

|-
|| 02:48
|| Note that as we change the angle, white arrows shifts their position.

|-
|| 02:55
|| This shift is also shown in the graph.

|-
|| 03:00
|| Scroll down the screen.

|-
|| 03:03
|| Here the conditions for maxima and minima are given.

|-
|| 03:08
||For more details please read the additional material provided in this tutorial.

|-
|| 03:15
|| Press '''F5''' key on the keyboard to reset the '''App'''.

|-
|| 03:20
|| Scroll up and increase the spacing between the slit to 2000 nanometer.

|-
|| 03:26
|| Now click on the '''Maxima '''drop down.

Here we will see more options for the '''k '''value.

|-
|| 03:36
|| Click on the '''Minima''' drop down.

|-
|| 03:38
|| Note that the first minima is formed at 8.6 degrees.

|-
||03:44
|| Click on the second minima that is''' k=2'''.

|-
|| 03:49
|| The white arrows shift to the second minima in both screen and graph.

|-
|| 03:56
|| Here the '''Relative intensity''' changes to zero(0).

|-
|| 04:01
||Zero indicates dark fringe.

|-
|| 04:05
||The waves superimpose and are out of phase to give zero intensity.

This is destructive interference.

|-
|| 04:15
|| Click on the '''Intensity profile''' radio button.

|-
|| 04:19
|| Here note that the red points indicate zero intensity.

|-
|| 04:25
|| Now click on '''Maxima '''drop down and select '''k=3'''.

|-
|| 04:32
|| The red point has shifted to the third peak.

|-
|| 04:36
||The '''Relative intensity''' has changed to 1.

|-
|| 04:41
||Here the waves superimpose to form a wave with maximum intensity.

|-
|| 04:48
||This is constructive interference.

This constructive interference results in a bright '''fringe'''.

|-
|| 04:56
|| Click on '''Interference pattern''' radio button at the bottom of the green panel.

|-
|| 05:03
|| Note that the interference graph shows equally spaced dark and bright fringes.

|-
|| 05:11
||Therefore the value of relative intensity only shows 0 and 1.

|-
|| 05:18
|| Press '''F5''' key on the keyboard to reset the '''App'''.

|-
|| 05:23
|| Let us calculate the value of angle for first maxima.

|-
|| 05:29
|| To do so we can rearrange the equation given in the interface

'''α <nowiki>= sin</nowiki><sup>-1</sup>(kλ/d)'''

|-
|| 05:41
|| Take the value of k as 1 since we have to calculate the angle for the first maxima.

|-
|| 05:49
||Take the value of wavelength and spacing between slit as shown on interface.

|-
|| 05:56
||Next substitute the values in the formula.

|-
|| 06:00
||The calculated value of angle of first maxima is 36.86 degree.

|-
|| 06:09
||Let us compare with the value shown in the '''App'''.

|-
|| 06:13
|| Click on the''' Maxima''' drop down and select '''k=1'''.

|-
|| 06:18
|| Observe that the value of the angle next to K=1 is 36.9 degrees.

|-
|| 06:27
||The value is comparable with the calculated value.

|-
||06:32
|| As an Assignment

Change the Spacing between slits to 3500 nm and Calculate the angle of fourth and fifth maxima.

|-
|| 06:45
|| Let us move on to the next '''App'''.

|-
|| 06:48
|| Follow the same steps as shown earlier while opening the''' App.'''

|-
|| 06:54
||The '''Diffraction of Light by a Single Slit '''opens on the screen.

|-
|| 07:00
|| This '''App''' shows the setup of diffraction through a single slit experiment.

|-
|| 07:06
||This set up is also known as '''Fraunhofer's Diffraction at a single slit'''.

|-
|| 07:12
|| scroll down to see the conditions for maxima and minima.

|-
|| 07:17
|| Scroll up and select '''Intensity profile''' radio button.

|-
|| 07:23
|| Observe that, only one central bright region is seen.

|-
|| 07:28
||This intensity decreases as we move away from the center.

|-
|| 07:34
|| In the green panel, click on the '''Width of slit '''text-box and enter 3000 nanometer.

|-
|| 07:42
|| Observe that a number of alternate dark and bright fringes are formed

|-
|| 07:48
|| Now click on the '''Maxima''' drop down.

|-
|| 07:51
||Observe that the central maxima is at 0 degrees.

|-
|| 07:57
||It shows '''Relative intensity''' as 1. This is the maximum intensity.

|-
||08:04
|| From the '''Maxima''' drop down select k=1.

|-
||08:09
|| Here the''' Relative intensity''' decreases from 1 to 0.0472.

|-
|| 08:18
|| Again click on '''Maxima''' drop down and select k=2.

|-
||08:25
|| The '''Relative intensity '''decreases to 0.0165.

|-
|| 08:32
|| Know Click on the''' Minima''' drop down and select k =2

|-
|| 08:38
|| The value of '''Relative intensity''' is shown as 0.

|-
|| 08:43
|| Click on '''Minima '''drop down and select k=4.

|-
|| 08:49
|| Note that for every dark fringe the value of relative intensity will remain zero.

|-
|| 08:57
|| Here I have made the table to show the relative intensity for maxima and minima.

|-
||09:05
|| Observe the relative intensity for maxima.

|-
|| 09:08
||The Relative intensity decreases as we move away from central region.

|-
|| 09:15
||For each minima, we have seen that the value remains zero for the relative '''intensity'''.

|-
|| 09:23
|| Drag the '''Wavelength slider '''to its highest value that is to 780 nm.

This is the region of red light.

|-
|| 09:34
|| Next click on '''Maxima '''drop down.

Here we see four bright fringes.

|-
|| 09:41
|| Next drag the slider of '''Wavelength''' to its lowest value that is to 380 nanometer.

This is the region of violet light.

|-
|| 09:53
|| Now click on the '''Maxima''' drop down.

|-
|| 09:56
||Here we can see eight positions for bright fringes.

|-
||10:01
|| This happens because violet light refracts more than red light.

|-
|| 10:07
||Hence we see more number of bright fringes for violet light.

|-
|| 10:13
|| Drag the '''Wavelength''' slider to 520 nm.

|-
|| 10:18
|| Click on '''Maxima''' drop down and select first bright fringe.

|-
|| 10:23
|| Here the first bright fringe is formed at an angle of 14.4 degrees.

|-
|| 10:31
|| Again drag the slider of '''Wavelength''' to 720 nanometer.

|-
|| 10:37
|| Click on the '''Maxima '''drop down and select K=1.

|-
|| 10:42
|| Here the first bright fringe is formed at an angle of 20.1 degrees.

|-
|| 10:49
||Hence we conclude that if we increase the wavelength, angle also increases.

|-
|| 10:56
|| Scroll down the screen.

This is shown in the formula.

|-
|| 11:02
|| Here, the angle is directly proportional to the wavelength.

|-
||11:07
|| As an assignment,

Change the wavelength to 380 nm and width of slit to 5000 nm.

|-
|| 11:17
||Use the table as shown earlier in this tutorial for your reference.

|-
|| 11:23
||Tabulate the total number of maxima and minima.

|-
||11:28
|| For each maxima tabulate the value of relative intensity from the App.

Explain the diffraction pattern

|-
|| 11:38
|| Differentiate between interference and diffraction patterns.

|-
|| 11:43
|| Let us summarize.
|-
|| 11:45
|| In this tutorial we have, Verified the relation between wavelength and relative intensity.

|-
|| 11:52
||Found the relation between slit width, maxima and minima.

|-
|| 11:58
||Calculated the angle for the given maxima.

|-
|| 12:03
||Interpreted diffraction intensity profile.

|-
|| 12:07
||Verified the relation between wavelength and angle.

|-
||12:12
|| These Apps are created by Walter-fendt and his team.

|-
|| 12:17
|| The video at the following link summarizes the Spoken Tutorial project.

Please download and watch it.

|-
|| 12:25
|| The '''Spoken Tutorial Project''' team, conducts workshops and gives certificates.

For more details, please write to us.

|-
|| 12:35
|| Please post your timed queries in this forum.

|-
||12:39
|| Spoken Tutorial Project is funded by MHRD, Government of India.

|-
|| 12:45
|| This is Himanshi Karwanje from IIT-Bombay.

Thank you for joining.
|-
|}

Apps-On-Physics/C3/Interference-and-Diffraction/English-timed - Revision history

PoojaMoolya: Created page with "{|border=1 |- || '''Time ''' || '''Narration''' |- || 00:01 || Welcome to the Spoken Tutorial on '''Interference and Diffraction'''. |- || 00:07 || At the end of this tutori..."