The following table of work functions for metals may be helpful for some of the problems...

  

    

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The following table of work functions for metals may be helpful for some of the problems in this homework: Aluminum 4.08 ev Cesium 2.1 ev Lead 4.14 eV Potassium 2.3 eV Uranium 3.6 eV 6.35 ev Zinc Beryllium 5.0 eV Cobalt 5.0 eV Magnesium 3.68 eV Platinum 4.3 eV Cadmium 4.07 ev Copper 4.7 ev Mercury 4.5 eV Selenium 5.11 ev Calcium 2.9 eV Gold 5.1 eV Nickel 5.01 ev Silver 4.73 eV Carbon 4.81 evron 4.5 ev Niobium 4.3 eV Sodium 2.28 ev To answer the following questions, you should use the Photoelectric Effect simulation. 1. Suppose you set up an experiment for observing photoelectric effect, so that the plate is ejecting electrons. Predict which of the following changes to the experiment could increase the maximum initial kinetic energy of the ejected electrons. (Select all that apply) Then test your prediction. Decreasing the intensity of the light beam Increasing the wavelength of light Decreasing the wavelength of light Increasing the frequency of light Decreasing the frequency of light Increasing the voltage of the battery Decreasing the voltage of the battery Replacing the target with a material that has a larger work function Replacing the target with a material that has smaller work function Increasing the intensity of the light beam 2. Suppose now you set up the experiment so that the light intensity is non-zero but the plate is NOT ejecting electrons. Predict which of the following changes to the experiment could make the plate start ejecting electrons? (Select all that apply) Then test your prediction. Increasing the intensity of the light beam Decreasing the intensity of the light beam Increasing the wavelength of light Decreasing the wavelength of light Increasing the frequency of light Decreasing the frequency of light Increasing the voltage of the battery Decreasing the voltage of the battery Replacing the target with a material that has a larger work function Increasing the voltage of the battery 0000 Decreasing the voltage of the battery Replacing the target with a material that has a larger work function Replacing the target with a material that has smaller work function Increasing the intensity of the light beam 2. Suppose now you set up the experiment so that the light intensity is non-zero but the plate is NOT ejecting electrons. Predict which of the following changes to the experiment could make the plate start ejecting electrons? (Select all that apply) Then test your prediction. Increasing the intensity of the light beam Decreasing the intensity of the light beam Increasing the wavelength of light Decreasing the wavelength of light Increasing the frequency of light Decreasing the frequency of light Increasing the voltage of the battery Decreasing the voltage of the battery Replacing the target with a material that has a larger work function Replacing the target with a material that has a smaller work function In the photoelectric effect experiment, the graph current vs battery voltage for a metal with light of a particular frequency shining on it looks like the curve below. This graph represents current vs voltage for 200 nm light shining onto Cadmium (Cd) which has a work function of 4.07 eV. Explain your reasoning for why this curve has the shape that it does. In your answer, you should address: Why is current level at V>0, why does current go to zero at some negative voltage and what determines that voltage, and why does current start decrease steadily at V<0? Real Observation Current 0 Battery Voltage f If you have the experiment set up so that electrons are being emitted from the metal plate, which of the following are true and false? True False As long as conditions do not change, all emitted electrons have the same initial kinetic energy. True False The work function for the metal is different for different electrons. True False The energy of the photons hitting the plate must be less than the work function of the metal. True False The electrons emitted with the largest initial kinetic energy are those that were the least tightly bound in the metal. 5. These essay questions are designed to help you understand how the observations from the photoelectric effect experiment lead to and make sense only with a photon model of light. The following are some key experiments from the photoelectric effect. For each, explain 1. what you observe 2. what conclusions you can draw about light and why, and (a) Light is shining on a metal and electrons are being emitted. You turn the intensity down very low. (b) Light is shining on a metal plate and electrons are being emitted. Without changing the intensity, you make the wavelength longer and longer. 6. What causes the electrons to be ejected from the left plate in this simulation? A. The force exerted on the electrons by the battery B. The beam of light shining on the plate C. Both A and B. D. Neither A nor B. 7. You have a plate of metal, but you have no idea what kind of metal it is. You come up with the brilliant idea of measuring the work function of this metal by using it as the target in a photoelectric effect experiment. You can perform this experiment virtually by selecting '???' as the target in the simulation. What is the work function, in 'eV', of the mystery metal? The following table of work functions for metals may be helpful for some of the problems in this homework: Aluminum 4.08 ev Cesium 2.1 ev Lead 4.14 eV Potassium 2.3 eV Uranium 3.6 eV 6.35 ev Zinc Beryllium 5.0 eV Cobalt 5.0 eV Magnesium 3.68 eV Platinum 4.3 eV Cadmium 4.07 ev Copper 4.7 ev Mercury 4.5 eV Selenium 5.11 ev Calcium 2.9 eV Gold 5.1 eV Nickel 5.01 ev Silver 4.73 eV Carbon 4.81 evron 4.5 ev Niobium 4.3 eV Sodium 2.28 ev To answer the following questions, you should use the Photoelectric Effect simulation. 1. Suppose you set up an experiment for observing photoelectric effect, so that the plate is ejecting electrons. Predict which of the following changes to the experiment could increase the maximum initial kinetic energy of the ejected electrons. (Select all that apply) Then test your prediction. Decreasing the intensity of the light beam Increasing the wavelength of light Decreasing the wavelength of light Increasing the frequency of light Decreasing the frequency of light Increasing the voltage of the battery Decreasing the voltage of the battery Replacing the target with a material that has a larger work function Replacing the target with a material that has smaller work function Increasing the intensity of the light beam 2. Suppose now you set up the experiment so that the light intensity is non-zero but the plate is NOT ejecting electrons. Predict which of the following changes to the experiment could make the plate start ejecting electrons? (Select all that apply) Then test your prediction. Increasing the intensity of the light beam Decreasing the intensity of the light beam Increasing the wavelength of light Decreasing the wavelength of light Increasing the frequency of light Decreasing the frequency of light Increasing the voltage of the battery Decreasing the voltage of the battery Replacing the target with a material that has a larger work function Increasing the voltage of the battery 0000 Decreasing the voltage of the battery Replacing the target with a material that has a larger work function Replacing the target with a material that has smaller work function Increasing the intensity of the light beam 2. Suppose now you set up the experiment so that the light intensity is non-zero but the plate is NOT ejecting electrons. Predict which of the following changes to the experiment could make the plate start ejecting electrons? (Select all that apply) Then test your prediction. Increasing the intensity of the light beam Decreasing the intensity of the light beam Increasing the wavelength of light Decreasing the wavelength of light Increasing the frequency of light Decreasing the frequency of light Increasing the voltage of the battery Decreasing the voltage of the battery Replacing the target with a material that has a larger work function Replacing the target with a material that has a smaller work function In the photoelectric effect experiment, the graph current vs battery voltage for a metal with light of a particular frequency shining on it looks like the curve below. This graph represents current vs voltage for 200 nm light shining onto Cadmium (Cd) which has a work function of 4.07 eV. Explain your reasoning for why this curve has the shape that it does. In your answer, you should address: Why is current level at V>0, why does current go to zero at some negative voltage and what determines that voltage, and why does current start decrease steadily at V<0? Real Observation Current 0 Battery Voltage f If you have the experiment set up so that electrons are being emitted from the metal plate, which of the following are true and false? True False As long as conditions do not change, all emitted electrons have the same initial kinetic energy. True False The work function for the metal is different for different electrons. True False The energy of the photons hitting the plate must be less than the work function of the metal. True False The electrons emitted with the largest initial kinetic energy are those that were the least tightly bound in the metal. 5. These essay questions are designed to help you understand how the observations from the photoelectric effect experiment lead to and make sense only with a photon model of light. The following are some key experiments from the photoelectric effect. For each, explain 1. what you observe 2. what conclusions you can draw about light and why, and (a) Light is shining on a metal and electrons are being emitted. You turn the intensity down very low. (b) Light is shining on a metal plate and electrons are being emitted. Without changing the intensity, you make the wavelength longer and longer. 6. What causes the electrons to be ejected from the left plate in this simulation? A. The force exerted on the electrons by the battery B. The beam of light shining on the plate C. Both A and B. D. Neither A nor B. 7. You have a plate of metal, but you have no idea what kind of metal it is. You come up with the brilliant idea of measuring the work function of this metal by using it as the target in a photoelectric effect experiment. You can perform this experiment virtually by selecting '???' as the target in the simulation. What is the work function, in 'eV', of the mystery metal?

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