Difference between revisions of "PhET/C3/Photoelectric-Effect/English-timed"

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|| In this tutorial we will learn- How to use Interactive '''PhET simulation''', '''Photoelectric Effect'''.
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|| Using this simulation, students will be able to- Study '''Photoelectric Effect'''.
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1. Study Photoelectric Effect.
  
 
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||Find '''Stopping potential''' and '''Work function'''.
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|| As an assignment, Calculate the work function for '''Zinc''', '''Copper''' and '''Calcium'''.
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|| Using this simulation, we have learnt,  About '''Photoelectric Effect'''.
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|| The '''Spoken Tutorial Project '''team: conducts workshops using spoken tutorials and
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|| The Spoken Tutorial Project team: conducts workshops using spoken tutorials and
  
 
gives certificates on passing online tests.
 
gives certificates on passing online tests.

Revision as of 18:00, 8 August 2018

Time Narration
00:01 Welcome to this tutorial on Photoelectric Effect, PhET simulation.
00:07 In this tutorial we will learn- How to use interactive PhET simulation, Photoelectric Effect.
00:15 To follow this tutorial, learners should be familiar with topics in high school science.
00:22 Here I am using-

Ubuntu Linux OS version 14.04

00:28 Java version 1.7.0
00:32 Firefox Web Browser version 53.02.2.
00:38 Using this simulation, students will be able to-

1. Study Photoelectric Effect.

00:44 2. Determine Threshold frequency.
00:47 3. Find Stopping potential and Work function.
00:51 4. Study the factors affecting current and energy of electrons.
00:56 When light of a particular frequency strikes a metal surface, electrons are ejected.
01:04 Ejected electrons are counted by a detector that measures their kinetic energy.
01:11 Use the given link to download the simulation.
01:15 I have already downloaded the Photoelectric Effect simulation to my Downloads folder.
01:22 Open the terminal.
01:24 At the prompt type cd Downloads and press enter.
01:29 Then type, java space hyphen jar space photoelectric_en.jar and press enter.
01:40 Photoelectric Effect simulation opens.
01:44 Do not close the terminal, it will kill the process.
01:49 Click Cancel to continue.
01:52 This is the interface of Photoelectric Effect simulation.
01:57 This screen has a menu bar, with menu items, File, Options and Help.
02:05 Options menu has two options, Show photons and Control photon number instead of intensity.
02:14 Screen has a lamp to shine light on the metal surface.
02:19 We can change Intensity and wavelength by dragging the respective sliders.
02:26 We can also input Intensity and wavelength values in their respective boxes.
02:33 Photoelectric Effect is carried out inside a vacuum chamber.
02:38 A vacuum chamber consists of - A metal surface and a detector to measure kinetic energy of electrons.
02:48 A battery and a current indicator are connected in the circuit.
02:53 Battery is provided with a Voltage slider.
02:58 A Play/Pause and Step buttons are at the bottom of the screen.
03:04 On the right-side of the screen, we can see, a Target drop down box to choose metals.
03:11 By default Sodium is selected as Target metal.
03:16 For accuracy in results let's move the Intensity slider to 50%.
03:23 In Options menu click on Show photons option.
03:28 Observe that light is shined in the form of photons.
03:34 Uncheck Show photons option.
03:36 By default the wavelength slider is at 400 nanometer.
03:42 Electrons are ejected as soon as light falls on Sodium metal surface.
03:48 There is no time lag between incident radiation and electrons emission.
03:54 These electrons flow towards a detector.
03:58 For 0 V (zero voltage) value of current is shown as 0.071.
04:05 Under Graphs we have the following check boxes -
04:09 Current Vs battery voltage
04:12 Current Vs light intensity
04:15 Electron energy Vs light frequency.
04:19 Click on Current vs battery voltage check box.
04:23 We see a graph of current vs battery voltage.
04:29 Notice a red dot on the graph.
04:32 Drag the voltage slider slowly from 0 to 6.00 volts.
04:38 Notice that current remains constant as we increase the voltage.
04:44 This is indicated by the red line.
04:48 As we increase the voltage, speed of photoelectrons increases.
04:53 Let us see how intensity of light affects the current.
04:58 Click on Current vs light intensity check box.
05:03 Drag the Intensity slider upto 90%.
05:08 Notice that current increases linearly with the increase in intensity.
05:14 This is indicated by the green line.
05:18 Increase in intensity of light increases the magnitude of photoelectric current.
05:24 Now Current value is shown as 0.127.
05:30 Drag the Intensity slider back to 50%.
05:35 Now click on Electron energy Vs light Frequency graph check box.
05:42 Drag the wavelength slider towards UV region.

Observe the graphs.

05:49 Notice that energy increases linearly with the increase in Frequency.
05:55 This is indicated by the blue line.
05:59 Observe the change in current.
06:02 Increase in frequency, increases the energy of photoelectrons.
06:08 As frequency increases, energy transfer from photons to electrons increases.
06:15 This results in increase in the kinetic energy of ejected electrons.
06:21 Now click on a Camera icon.
06:24 A snapshot window opens.
06:27 It gives information about Graphs and Experimental Parameters.
06:33 Using this snapshot, we can compare graphs with different settings.
06:39 Close the snapshot window.
06:42 Now we will discuss how to calculate the Threshold Frequency.
06:48 Each metal has a characteristic minimum frequency to cause photoelectric emission.
06:55 This frequency is, Threshold Frequency, denoted by ʋ0.
07:01 Below the Threshold Frequency, Photoelectric Effect is not observed.
07:07 Drag the wavelength slider towards visible region.
07:12 Observe the wavelength at which electron ejection stops.
07:18 Notice that at 540 nm no more electrons are ejected from Sodium.
07:25 Let's type 539 nm in the wavelength text box and observe.
07:32 At 539 nm electrons start ejecting from sodium metal surface.
07:39 It means that, 539 nm is threshold wavelength for Sodium.
07:45 Here, value of current is 0.00.
07:49 Now let us calculate the threshold frequency value.
07:54 Here wavelength is shown in nano metres(nm).
07:58 I will convert it to metres by multiplying with 10 to the power of -9
08:05 Threshold frequency can be calculated using following formula.
08:10 Threshold frequency of sodium is 0.56 x 10 to the power of 15 </sup>Hz.
08:18 Now let us select Platinum as Target.
08:22 Click on drop down arrow and select Platinum.
08:26 At this wavelength we do not see ejection of photoelectrons.
08:31 Drag the slider to UV region untill electron ejection starts.
08:39 Drag the wavelength slider to lower wavelength region.
08:45 Notice that a large number of electrons with different energies are ejected.
08:52 To view electrons with highest energy, click on Show only highest energy electrons check box.
09:00 Uncheck the box to show electrons with different energies.
09:05 As an assignment, Calculate the Threshold Frequency of Platinum.
09:11 We will move on to the calculation of work function and stopping voltage.
09:17 Work function is minimum amount of energy necessary to start photoelectric emission.
09:24 Different metals have different values of work function.
09:29 It is denoted by ϕ0.
09:32 Work function is given by ϕ0= hʋ0.
09:38 Elements with low Ionization enthalpy values have low work function.

Example: Lithium, Sodium, Potassium, Rubidium, and Caesium.

09:51 Let us calculate the work function for Sodium.
09:55 Work function is calculated by using following formula.

w0 = hʋ0

10:04 Work function for Sodium is 2.31eV.(electron volts)
10:10 Similarly work function for Calcium is 2.9 eV (electron volts)
10:17 Stopping Potential- It is a negative voltage required to stop electrons from reaching the other side.
10:26 At Stopping Potential, photoelectric current becomes zero.
10:31 Let's see how to determine the stopping potential for Sodium.
10:37 Change Sodium as target metal.
10:41 Drag the wavelength slider to threshold wavelength of sodium.

That is 539 nanometer.

10:51 Drag the voltage slider to negative voltage.
10:56 At which voltage, electrons will bounce off from detector?
11:01 At -0.01 V(volts), electrons start to bounce off from detector.
11:08 Observe At -0.04 Volts, no electrons are ejected from sodium.
11:16 As an assignment, Calculate the work function for Zinc, Copper and Calcium.
11:22 Determine the stopping potential for the same metals.
11:27 Let us summarize. In this tutorial we have learnt about,

Photoelectric Effect, PhET simulation.

11:36 Using this simulation, we have learnt, About Photoelectric Effect.
11:41 To determine Threshold Frequency.
11:44 To find Stopping Potential and Work Function and
11:48 Study the factors affecting current and energy of electrons.
11:54 The video at the following link summarizes the Spoken Tutorial project.

Please download and watch it.

12:03 The Spoken Tutorial Project team: conducts workshops using spoken tutorials and

gives certificates on passing online tests.

12:13 For more details, please write to us.
12:17 Please post your timed queries on this forum.
12:22 This project is partially funded by Pandit Madan Mohan Malaviya National Mission on Teachers and Teaching.
12:31 Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.

More information on this mission is available at this link.

12:43 This is Meenal Ghoderao from IIT Bombay.

Thank you for joining.

Contributors and Content Editors

Madhurig, PoojaMoolya, Sandhya.np14

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