PhET/C2/Color-Vision/English-timed
From Script | Spoken-Tutorial
| 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. |
