PhET/C2/Color-Vision/English-timed

Time	Narration
00:01	Welcome to this tutorial on Color Vision, an interactive PhET simulation.
00:08	In this tutorial, we will demonstrate, Color Vision, an interactive PhET simulation.
00:17	Here I am using, Ubuntu Linux Operating System version 16.04
00:25	Java version 1.8.0
00:29	Firefox Web Browser version 60.0.2
00:35	Learners should be familiar with high school physics and biology.
00:41	Using this simulation, we will look at colour vision when the human eye sees: White light
00:50	Light of different colours from the visible spectrum
00:55	Light and filters of different colours of the visible spectrum
01:00	Red, green and blue light, separately or in combination
01:06	Please refer to the additional material provided with this tutorial. Let us begin.
01:14	Visible Light A portion of the electromagnetic spectrum is detected by human eye as visible light.
01:25	This portion extends from 380 to 760 nanometers'.
01:33	The colours of the visible spectrum can be remembered as VIBGYOR.
01:39	Violet, indigo, blue, green, yellow, orange, red
01:47	The lowest wavelength (highest frequency) appears violet.
01:53	The highest wavelength (lowest frequency) appears red.
01:59	Combining all the colours gives white light.
02:04	Use the given link to download the simulation.
02:09	I have already downloaded the Color Vision simulation to my Downloads folder.
02:16	To open the simulation, right click on the color-vision_en.html file.
02:23	Select the Open With Firefox Web Browser option. The file opens in the browser.
02:32	This is the interface for the Color Vision simulation.
02:37	Now we will explore the interface.
02:41	The interface has two screens Single Bulb RGB Bulbs
02:49	Click on Single Bulb screen.
02:53	In the Single Bulb screen, you can see a person facing the right. Just below the neck are two small images.
03:04	The first one is highlighted. It allows you to see the person’s face.
03:11	Click on the second image. On being highlighted, it shows the cross-section of the person’s brain.
03:20	Observe the optic nerves extending from the eyes into different parts of the brain.
03:28	Color Vision, Cone cells are photoreceptors in the retina that are sensitive to a range of wavelengths.
03:39	The leaf absorbs all wavelengths of visible light except green light.
03:46	Green light of 520 nanometers wavelength is reflected and reaches the eye.
03:54	Here, it activates the M or gamma type cones.
03:59	The visual information is sent from cones to retinal ganglia via the optic nerve.
04:07	The two optic nerves meet and cross over each other at the optic chiasma.
04:14	Now called optic tracts, they enter and synapse in the thalamus.
04:21	They then continue to the primary visual cortex in the occipital lobe in the back of the brain.
04:30	Let us return to the simulation.
04:34	Observe the ellipses above the person’s head.
04:39	They will be filled with the colour that the person sees.
04:44	Note the Play/Pause button at the bottom and the Step button next to it.
04:51	The Reset button will take us back to the start.
04:55	Observe the torch or flashlight in front of the person’s eyes.
05:01	The red button on the flashlight will switch it off and on.
05:06	Click on the first bulb above the flashlight.
05:11	This is white light. Click on the red button of the flashlight.
05:18	The first image below the flashlight is highlighted by default.
05:24	This will show the light as a beam.
05:28	Click on the second image below the flashlight.
05:33	This will show the light in the form of photons.
05:38	Click on the Pause button. Observe that the Step button is active.
05:45	Click on the Step button to see the photons move in a stepwise manner.
05:51	Click on the first image to return to the beam from the flashlight.
05:57	Observe the white ellipses above the person’s head.
06:02	This means that the person sees white light coming out of the flashlight.
06:08	Click on the second bulb above the flashlight. Observe the slider Bulb Color containing all colours of the visible spectrum.
06:19	Drag the Bulb Color slider from end to end.
06:24	The colour on which the handle is placed indicates the colour of the light from the flashlight.
06:31	Observe that the ellipses above the person’s head fill with the same colour.
06:38	You can change the colour that the person sees by dragging the Bulb Color slider. Drag the Bulb Color slider to red at the right end.
06:50	Note that there is a toggle switch in front of the person. It is connected to the Filter Color slider.
06:59	Observe that the Filter Color slider also contains the colours of the visible spectrum.
07:06	Click on the toggle switch. Observe that a filter appears in the path of the beam from the flashlight.
07:16	Drag the Filter Color slider from end to end.
07:21	The colour on which the handle is placed indicates the colour of the filter.
07:28	Note the filter is red and transmits a red beam. The person also sees red light.
07:38	Drag the Bulb Color slider to violet. Violet light comes out from the flashlight.
07:56	But with red as the Filter Color, no light is transmitted to the person.
07:52	The person does not see any light.
07:56	Drag the Filter Color slider to violet at the left end.
08:02	Note the filter becomes violet and violet light is transmitted to the person. The person now sees violet light.
08:13	Drag the Bulb Color slider to red at the right end.
08:19	Observe how the filter remains violet but the light beam is now red.
08:26	But the violet filter does not transmit the red light. The person sees no light.
08:35	Drag both sliders to different colours to see whether light is transmitted to the person.
08:43	Observe how light is only transmitted when both sliders are set at the same or nearly same colour.
08:53	The filter subtracts all wavelengths and only transmits the wavelength of its own colour.
09:01	Transmission is weaker for wavelengths very close to and maximum for the filter’s colour.
09:09	As an assignment, Choose white light to come from the flashlight and observe the transmission of light from the filter.
09:22	Now, let us click on the RGB Bulbs screen at the bottom of the interface.
09:29	Here, too, you can see the person facing the right. Click on the second image which allows you to see the cross-section of the person’s brain.
09:41	The Play/Pause, Step and Reset buttons are all seen at the bottom of the interface.
09:49	Three sliders and three flashlights are seen on the screen. All sliders are set at the minimum levels.
10:00	The uppermost one is a red slider, the second green and the lowermost one is a blue slider.
10:10	Drag the red slider to the maximum level.
10:15	Note how red photons come out of the flashlight next to the red slider.
10:22	The photons reach the person’s eye and the person sees red light.
10:28	Drag the green slider to the maximum level. Note how red and green photons come out of the flashlights next to the red and green sliders.
10:41	Red and green add to give yellow. The cones sensitive to red and green light are activated so that the person sees yellow.
10:53	Click the Pause button.
10:56	Drag the blue slider to the maximum level.
11:00	Click on Play button. Observe how all three colours mix so that the person sees white light.
11:11	Let us summarize.
11:14	In this tutorial, we have demonstrated how to use the Color Vision PhET simulation.
11:22	Using this simulation, we looked at colour vision when the human eye sees: White light
11:31	Light of different colours from the visible spectrum
11:35	Light and filters for different colours of the visible spectrum
11:40	Red, green and blue light, separately or in combination
11:46	As an assignment,Adjust the red, blue and green sliders to get these 6 colours.
11:55	Which RGB combination would you pick to design these schemes?
12:01	Look for an image of the colour wheel on the Internet.
12:06	Pick colour combinations for the following schemes.
12:11	The video at the following link summarizes the Spoken Tutorial project. Please download and watch it.
12:20	The Spoken Tutorial Project team conducts workshops using spoken tutorials and gives certificates on passing online tests. For more details, please write to us.
12:35	Please post your timed queries in this forum.
12:40	This project is partially funded by Pandit Madan Mohan Malaviya National Mission on Teachers and Teaching.
12:49	Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India. More information on this mission is available at this link.
13:03	This is Vidhya Iyer from IIT Bombay, signing off. Thank you for joining.

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