Difference between revisions of "PhET/C3/Photoelectric-Effect/English"
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point to Detector. | point to Detector. | ||
| − | || A vacuum chamber | + | || A vacuum chamber consists of - |
A metal surface and a detector to measure kinetic energy of electrons. | A metal surface and a detector to measure kinetic energy of electrons. | ||
| Line 362: | Line 362: | ||
Point to the ejected electrons. | Point to the ejected electrons. | ||
| − | || | + | || Drag the wavelength slider to lower wavelength region. |
Notice that a large number of electrons with different energies are ejected. | Notice that a large number of electrons with different energies are ejected. | ||
| Line 381: | Line 381: | ||
|- | |- | ||
|| | || | ||
| − | || | + | || we will move on to the calculation of '''work function''' and '''stopping voltage'''. |
|- | |- | ||
|| '''Slide Number 11''' | || '''Slide Number 11''' | ||
Latest revision as of 15:21, 12 August 2022
| Visual Cue | Narration |
| Slide Number 1
Title slide |
Welcome to this tutorial on Photoelectric Effect, PhET simulation. |
| Slide Number 2
Learning objectives |
In this tutorial we will learn-
How to use Interactive PhET simulation, Photoelectric Effect. |
| Slide Number 3
Pre-requisites |
To follow this tutorial,
Learners should be familiar with topics in high school science. |
| Slide Number 4
System Requirements |
Here I am using-
Ubuntu Linux OS version 14.04 Java version 1.7.0 Firefox Web Browser version 53.02.2. |
| Slide Number 5
Learning Goals |
Using this simulation, students will be able to-
Study Photoelectric Effect. Determine Threshold frequency. Find Stopping potential and Work function. Study the factors affecting current and energy of electrons. |
| Slide Number 6
Photoelectric Effect |
When light of a particular frequency strikes a metal surface, electrons are ejected.
Ejected electrons are counted by a detector that measures their kinetic energy. |
| Slide Number 7
Link for PhET simulation |
Use the given link to download the simulation. |
| Point to Photoelectric Effect phet. | I have already downloaded the Photoelectric Effect simulation to my Downloads folder. |
| To open java file,
Press Ctrl+Alt+T keys. Type cd Downloads and press enter. Type java space hyphen jar photoelectric_en.jar and press enter. Point to interface. |
Open the terminal.
At the prompt type cd Downloads and press enter. Then type, java space hyphen jar space photoelectric_en.jar and press enter. Photoelectric Effect simulation opens. |
| Note.
Point to the terminal. Click Cancel. |
Do not close the terminal, it will kill the process.
Click Cancel to continue. |
| Point to the interface. | This is the interface of Photoelectric Effect simulation. |
| Point to File, Options and Help.
Click on Options menu. Point to Show photons and Control photon number instead of intensity. |
This screen has a menu bar, with menu items,
File, Options and Help. Options menu has two options, Show photons and Control photon number instead of intensity. |
| Point to lamp. | Screen has a lamp to shine light on the metal surface. |
| Point to Intensity and wavelength sliders.
Point to Intensity and wavelength texboxes. |
We can change Intensity and wavelength by dragging the respective sliders.
We can also input Intensity and wavelength values in their respective boxes. |
| Point to vacuum chamber. | Photoelectric Effect is carried out inside a vacuum chamber. |
| Point to vacuum chamber.
point to metal surface. point to Detector. |
A vacuum chamber consists of -
A metal surface and a detector to measure kinetic energy of electrons. |
| Point to battery and current indicator
Point to voltage slider. |
A battery and a current indicator are connected in the circuit.
Battery is provided with a Voltage slider. |
| Point to Play/Pause and Step buttons. | A Play/Pause and Step buttons are at the bottom of the screen. |
| Point to and scroll down Target drop down box.
Point to Sodium Target. |
On the right-side of the screen, we can see, a Target drop down box to choose metals.
By default Sodium is selected as Target metal. |
| Drag the Intensity slider to 50%.
Click on Show photons option. Point to the photons. Uncheck Show photons option. |
For accuracy in results let's move the Intensity slider to 50%.
In Options menu click on Show photons option. Observe that light is shined in the form of photons. Uncheck Show photons option. |
| Point to wavelength slider at 400nm.
Point to electrons. Point to detector. |
By default the wavelength slider is at 400nm.
Electrons are ejected as soon as light falls on Sodium metal surface. There is no time lag between incident radiation and electrons emission. These electrons flow towards a detector. |
| Point to current. | For 0 V (zero voltage) value of current is shown as 0.071. |
| Point to Graphs check boxes. | Under Graphs we have the following check boxes -
Current Vs battery voltage Current Vs light intensity Electron energy Vs light frequency. |
| Click on Current vs battery voltage check box.
Point to graph. Point to the red dot. |
Click on Current vs battery voltage check box.
We see a graph of current vs battery voltage. Notice a red dot on the graph. |
| Drag the voltage slider from 0 to 6.00 volts.
Point to Graph. Point to red line. Point to electrons. |
Drag the voltage slider slowly from 0 to 6.00 volts.
Notice that current remains constant as we increase the voltage. This is indicated by the red line. As we increase the voltage, speed of photoelectrons increases. |
| Click on Current vs light intensity check box.
Drag the Intensity slider upto 90%. |
Let us see how intensity of light affects the current.
Click on Current vs light intensity check box. Drag the Intensity slider upto 90%. |
| Point to graph.
Point to green line. |
Notice that current increases linearly with the increase in intensity.
This is indicated by the green line. |
| Increase in intensity of light increases the magnitude of photoelectric current. | |
| Point to current meter. | Now Current value is shown as 0.127. |
| Drag the Intensity slider to 50%. | Drag the Intensity slider back to 50%. |
| Click on Electron energy VS light Frequency graph check box. | Now click on Electron energy Vs light Frequency graph check box. |
| Drag the wavelength slider towards UV region.
Point to graphs. Point to blue line Point to current value. |
Drag the wavelength slider towards UV region.
Observe the graphs. Notice that energy increases linearly with the increase in Frequency. This is indicated by the blue line. Observe the change in current. Increase in frequency, increases the energy of photoelectrons. |
| Point to the graph. | As frequency increases, energy transfer from photons to electrons increases.
This results in increase in the kinetic energy of ejected electrons. |
| Click on Camera icon.
Point to snapshot window. Point to Graphs. Click on close button. |
Now click on a Camera icon.
A snapshot window opens. It gives information about Graphs and Experimental Parameters. Using this snapshot, we can compare graphs with different settings. Close the snapshot window. |
| Now we will discuss how to calculate the Threshold Frequency. | |
| Slide Number 8
Threshold frequency |
Each metal has a characteristic minimum frequency to cause photoelectric emission.
This frequency is, Threshold Frequency, denoted by ʋ0. Below the Threshold Frequency, Photoelectric Effect is not observed. |
| Drag the wavelength slider towards visible region. | Drag the wavelength slider towards visible region.
Observe the wavelength at which electron ejection stops. |
| Point to 540 nm. | Notice that at 540 nm no more electrons are ejected from Sodium. |
| Type 539 nm in wavelength texbox.
point to Current meter. point to electrons. Point to 539 nm. Point to Current meter. |
Let's type 539 nm in the wavelength text box and observe.
At 539 nm electrons start ejecting from sodium metal surface. It means that, 539 nm is threshold wavelength for Sodium. Here, value of current is 0.00. |
| Now let us calculate the threshold frequency value. | |
| Slide Number 9
Threshold frequency calculation for sodium. 539 nm = 539 x 10-9 m. Frequency can be calculated using following formula. c= ʋλ, ʋ = c/λ ʋ = (3 x 108m/s)/ (539 x 10-9m) ʋ= 0.56 x 1015Hz. |
Here wavelength is shown in nano metres(nm).
I will convert it to metres by multiplying with 10-9. Threshold frequency can be calculated using following formula. Threshold frequency of sodium is 0.56 x 1015 Hz. |
| Click on drop down arrow and select Platinum. | Now let us select Platinum as Target.
Click on drop down arrow and select Platinum. |
| Point to the wavelength value.
Drag the slider to UV region. |
At this wavelength we do not see ejection of photoelectrons.
Drag the slider to UV region untill electron ejection starts. |
| Drag the wavelength slider to lower wavelength region.
Point to the ejected electrons. |
Drag the wavelength slider to lower wavelength region.
Notice that a large number of electrons with different energies are ejected. |
| Click on Show only highest energy electrons check box.
Uncheck the box. |
To view electrons with highest energy, click on Show only highest energy electrons check box.
Uncheck the box to show electrons with different energies. |
| Slide Number 10
Assignment |
As an assignment,
Calculate the Threshold Frequency of Platinum. |
| we will move on to the calculation of work function and stopping voltage. | |
| Slide Number 11
Work Function |
Work function is minimum amount of energy necessary to start photoelectric emission.
Different metals have different values of work function. It is denoted by ϕ0. |
| Slide Number 12
Work function |
Work function is given by ϕ0= hʋ0.
Elements with low Ionization enthalpy values have low work function. Example: Li, Na, K, Rb, and Cs. |
| Slide Number 13
Work function for Sodium For Sodium, Ʋ0 = 0.56 x 1015 hZ which we have calculated earlier. w0 = hʋ0 w0 = 6.626 x 10-34x0.56x1015 w0 = 6.626 x 0.56 x 10-19 w0 = 3.711 x 10-19 J w0 =3.711 x 10-19 / 1.60218 x 10-19 w0 =2.31 eV |
Let us calculate the work function for Sodium.
Work function is calculated by using following formula. w0 = hʋ0 Work function for Sodium is 2.31eV.(electron volts) |
| Slide Number 14
Work function for Calcium Formula for work function is w0 = hʋ0 For Calcium, Ʋ0 =0.703 x 1015 hZ w0 = hʋ0 w0 = 6.626 x 10-34 x 0.703 x 1015 w0 = 6.626 x 0.703 x 10-19 w0 = 4.66 x 10-19/1.6021 X 10-19 wo=2.9 eV |
Similarly work function for Calcium is 2.9 eV (electron volts) |
| Slide Number 15
Stopping potential |
Stopping Potential-
It is a negative voltage required to stop electrons from reaching the other side. At Stopping Potential, photoelectric current becomes zero. |
| Click on drop down arrow and select Sodium.
Drag wavelength slider to 539 nm. |
Let's see how to determine the stopping potential for Sodium.
Change Sodium as target metal. Drag the wavelength slider to threshold wavelength of sodium. That is 539 nm. |
| Drag the voltage slider to negative voltage.
Point to electrons. Point to -0.04 V and electrons. |
Drag the voltage slider to negative voltage.
At which voltage, electrons will bounce off from detector? At -0.01 V(volts), electrons start to bounce off from detector. Observe At -0.04 V, no electrons are ejected from sodium. |
| Slide Number 16
Assignment |
As an assignment,
Calculate the work function for Zinc, Copper and Calcium. Determine the stopping potential for the same metals. |
| Slide Number 17
Summary |
Let us summarize.
In this tutorial we have learnt about, Photoelectric Effect, PhET simulation. |
| Slide number 18
Summary |
Using this simulation, we have learnt,
|
| Slide Number 19
About Spoken Tutorial project |
The video at the following link summarizes the Spoken Tutorial project.
Please download and watch it. |
| Slide Number 20
Spoken Tutorial workshops |
The Spoken Tutorial Project team:
conducts workshops using spoken tutorials and gives certificates on passing online tests. For more details, please write to us. |
| Slide Number 21
Forum for specific questions: Do you have questions in THIS Spoken Tutorial? Please visit this site. Choose the minute and second where you have the question. Explain your question briefly. Someone from our team will answer them. |
Please post your timed queries on this forum. |
| Slide Number 22
Acknowledgement |
This project is partially funded by Pandit Madan Mohan Malaviya National Mission on Teachers and Teaching. |
| Slide Number 23
Acknowledgement |
Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.
More information on this mission is available at this link. |
| This is Meenal Ghoderao from IIT Bombay.
Thank you for joining. |
