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Download Photoelectric Effect - Data Analysis Exercise
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The Photoelectric Effect Demonstration http://phet.colorado.ed.au/en/simulation/photoelectric First, with the circuit set up so that the battery is attracting electrons: 1. The photoelectric effect occurs when ______________ shines on a metal. Electrons can absorb the energy from the light. If there is enough energy, they can __________ ___________ from the metal and become free electrons. They are now called ______________ The photoelectric effect was first observed in 1887 by Heinrich Hertz. 2. Draw a rough outline of the circuit. Include space here 3. When electrons are ejected from the surface of the metal, they all make it across the gap to the other side because the other terminal is ___________ ,and the electrons are _____________ to it. 4. With the light set on ultraviolet ( = 360 nm), what is the effect of changing the intensity (brightness)? Include space here 5. With the light set on red light ( = 70 nm), what is the effect of changing the intensity? Include space here 6. What effect does changing the frequency/wavelength have? Include space here 7. For sodium, what is the threshold wavelength and threshold frequency? Include space here 8. For zinc, what is the threshold wavelength and threshold frequency? Include space here 9. Below the threshold frequency, _____________ electrons are ejected, no matter how intense (bright) the light source is. Above the threshold frequency, electrons are _____________ ejected, no matter how dim the light source is. Next, with the circuit set up so that the battery is repelling electrons: 1. Draw a rough outline of the circuit. Include space here 2. When electrons are ejected from the surface of the metal, they ________ _________ all make it across the gap to the other side. This is because the anode is __________, so it ____________ the electrons. Only the electrons with the most energy (the fastest electrons) can make it across. 3. For sodium, with the wavelength on 400 nm, what is the stopping potential? Include space here 4. The stopping potential (stopping voltage) is the ____________ voltage needed to stop ALL of the electrons from getting across. 5. The stopping potential gives us an indication of the maximum ___________ ____________of the electrons. 6. For sodium, with the wavelength on 360 nm (ultraviolet), what is the stopping potential? What is the maximum kinetic energy of the photoelectrons? Include space here 7. Does the intensity affect the stopping potential? So, does the intensity affect the maximum kinetic energy of the electrons? Include space here 8. What effect does changing the intensity of the light have on the experiment? Include space here 9. What effect does changing the frequency of the light have on the experiment? Include space here Problems with the Wave Model of light!!! The wave model of light predicts that the energy of a light wave is found from its ______________ So the kinetic energy of the electrons should be affected by the __________ of the light. The wave model also predicts that the frequency of the light should have ________ ____________on the energy. But this is not observed! So something is wrong with the wave model! To overcome these problems, Albert Einstein suggested that light comes in tiny packets or particles called __________ , and the energy of these photons is given by: ____________