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Simulate photoelectric effect

 

You are now going to work with a simulation of the photoelectric effect. You will get questions and problems to respond to along the way.

Open the simulation (opens in a new tab)

 

Start by choosing zinc (Zn) as the cathode material.

Note that you can vary the intensity (I) and wavelength (λ) of the incoming light and the voltage (U) of the battery. You can also read the current (Ianode) that flows in the circuit.

Writing task 2A

Set the intensity to 5 W/m2, and set the voltage to 0 V.

Start the simulation.

  1. What happens when you change the wavelength of the incoming light?
  2. Write down the relation between the wavelength and the energy of a photon.
  3. What must the wavelength be in order for electrons to be emitted from zinc?
  4. What must the energy  (Ephoton) of the photons be?
  5. Check that the energy reading, Ephoton, agrees with what you can calculate from the relation in point 2.
  6. The largest light frequency that can get electrons emitted is called the threshold frequency. Determine the threshold frequency. 
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Writing task 2B

Set the voltage to 0 V and the wavelength to 250 nm.

  1. What happens to the current, Ianode, when you change the intensity of the incoming light?
  2. Keep the voltage at 0 V, but set the wavelength to 400 nm. What happens to the current when you now change the intensity of the incoming light?
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Writing task 2C

Explain why the intensity of the light makes a difference for certain wavelengths, but not for others.

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Writing task 2D

Set the wavelength to 270 nm and the intensity to 10 W/m2. 

  1. What happens when you change the voltage?
  2. Notice that for a certain voltage, the electrons just barely reach the anode. We call this the stopping voltage or stopping potential. What is the stopping voltage?
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Writing task 2E

Set the intensity to 10 W/m2 and the voltage to 0 V.

1. Use the simulation and make a table (for instance in Excel). The table should contain  wavelength, frequency og kinetic energy as shown below.

Fill in your own table with increasing wavelengths.

Wavelength, λ (nm) 150 ... ... ...
Frequency, f (1015Hz) 2,0 ... ... ...
Kinetic energy (10-19J) 6,30 ... ... ...

 

2. Make a graph of kinetic energy as a function of frequency.

Einstein’s equation for photoelectric effect may be written like this:

Ek = hf - W

Here Ek Ek is kinetic energy and W is the work function. The work function is the minimum amount of energy required for an electron to be emitted from the cathode material, in this case zinc. In the simulation you can see that the work function for zinc is 6,94∙10-19 J.

3. Make a point in your graph that marks the work function.

4. Use your graph to find a value for the Planck constant.

5. Use your graph to find the threshold frequency (see also exercise 2A, point 6

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