ntroductory Videos:

1.Wave Particle Duality and Photoelectric Effect

2.Photoelectric Effect

3.Photoelectric Effect Demonstration

4.Another Demonstration of Photoelectric Effect

5.Theoretical Explanation of Photoelectric Effect

Read the CANVAS lab manual to answer questions. If you have any difficulties understanding any concept, reach out to your instructor.

After watching the videos mentioned above and studying the CANVAS lab manual, answer the following questions:

1. What is the relation between wavelength and energy?

2. Let’s say we have an unknown metal and the value of its work function is 3.14 eV. The light we are using, its intensity is 70%. What is the minimum energy needed to eject an electron from that metal? [1eV (electronvolt) = 1.6 x 10-19 J, Electronvolt is a unit of energy; To learn more about eV, you may go through this link ]

3. Now, let’s say you are observing electrons are ejected from that metal. If you increase the intensity of that light beam to 90%, will there be any change in the number of ejected electrons?

Now, answer the following questions using the interactive simulation in the link below:

Photoelectric Simulation 1

When you first open the link, you will see a purple color light beam and you will also observe electrons ejected from the metal which is represented by blue balls. Now, click on the “Change Metal” option and select Calcium (Ca). Then go to the option “Select V” and choose Voltage, V = 0. After that, on the right side, click on the “Select Intensity” option and make the intensity of light to 10%. After that, select = 900nm. [Here, means wavelength and 1nm = 10-9 m]

4. What is the energy of the light beam? Do you observe any electrons ejected from the Calcium plate? Explain your answer.

5. Keeping the same intensity, start changing the wavelength. Mention the wavelength when you have started observing electrons.

(a)Calculate the energy of the beam.

(b) Compare the energy of the beam with the work function, Φ of Calcium (The value of the work function is written in the bottom left of the screen). Explain the reason behind the observation of ejected electrons. [1eV (electron volt) = 1.6 x 10-19 J ]

6. Keeping the same configuration, write down the value of current in the ampere (the unit of current) that you observe in the ammeter.

7. Now, just change the intensity of light from 10% to 80%? Do you observe any differences? If so, write down the differences and explain the reason behind your observation.

8. Change the voltage to 0.5V. Do you get different values for the current? Give an explanation of your answer.

9. Increase the voltage to 1V, 2V, and 2.5V. Is there any change in current? Justify your answer.

10. Keeping all the other configurations as it was, just change the voltage to V = – 0.5 V. What are you observing and why?

11. Now, click on the “select” option on the top left of your screen, choose “world and I vs V”. You will observe a plot of “current vs voltage” on the right side of the screen. From that plot, determine an “approximate” value of the stopping voltage for Calcium.

Now, answer the following questions using the interactive simulation in the link below:

Photoelectric Effect Simulation 2

Here you will be observing the Photoelectric effect for Sodium. You will observe ejected electrons. Do not change any configuration.

12. Change the wavelength of the incident photon beam so that the current becomes zero.

(a) Write down the corresponding wavelength and the frequency. Calculate the energy in eV from that information.

(b) Do you think this energy is equal to the work function of Sodium? Justify your answer. [1eV (electron volt) = 1.6 x 10-19 J ]

13. Now on the top left side, click on the “options”. Then click on the “Metals” option. Then choose “Iron”. Now change the wavelength and find the maximum value of wavelength so that the Iron plate starts ejecting electrons.

(a)Mention the wavelength and frequency.

(b)Calculate the energy of the light beam in eV. Then do the same for Carbon and Gold. [1eV (electron volt) = 1.6 x 10-19 J ]