## Names:____________________________________________________

physical代写 To be able to explain how the photoelectric effect experiment works and why a photon model of light is necessary to explain the results.

### Learning Goal: physical代写

To be able to explain how the photoelectric effect experiment works and why a photon model of light is necessary to explain the results.physical代写

#### 1.Suppose you set up the experiment 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.physical代写

A. Increasing the intensity of the light beam                                                                            B. Decreasing the intensity of the light beam

C. Increasing the wavelength of light                                                                                         D. Decreasing the wavelength of light

E. Increasing the frequency of light                                                                                            F. Decreasing the frequency of light

G. Increasing the voltage of the battery                                                                                     H. Decreasing the voltage of the battery

I. Replacing the target with a material that has a larger work function                              J. Replacing the target with a material that has a smaller work function

#### 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.physical代写

A. Increasing the intensity of the light beam                                                                           B. Decreasing the intensity of the light beam

C. Increasing the wavelength of light                                                                                        D. Decreasing the wavelength of light

E. Increasing the frequency of light                                                                                           F. Decreasing the frequency of light

G. Increasing the voltage of the battery                                                                                    H. Decreasing the voltage of the battery

I. Replacing the target with a material that has a larger work function                             J. Replacing the target with a material that has a smaller work function

#### 3.What causes the electrons to be ejected from the left plate in this simulation?physical代写

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.

#### 4.(Free Response) This section is 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 key experiments from the photoelectric effect. For each, explain   physical代写

• what you observe
• what conclusions you can draw about light and why, and
• how it is or is not consistent with what you would expect to observe if light matched the classical wave model and with what you would expect to observe if it matched the photon model of light.

a. Light is shining on a metal and electrons are being emitted. You turn the intensity down very, 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.

#### 5.If you have the experiment set up so that electrons are being emitted from the metal plate, which of the following are true or false?physical代写

• As long as conditions do not change, all emitted electrons have the same initial kinetic energy. T/F
• The work function for the metal is different for different electrons. T/F
• The energy of the photons hitting the plate must be less than the work function of the metal. T/F
• The electrons emitted with the largest initial kinetic energy are those that were the least tightly bound in the metal. T/F

### Let’s study Sodium:  physical代写

1. #### In the photoelectric effect experiment, the graph of 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 voltagefor 200nm light shining onto Cadmium (Cd) which has a work function of 4.07 eV.physical代写

• Explain your reasoning for whythis 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 decreasing steadily at V<0?

• What is the stopping potential in this situation (in eV)? (Remember stopping voltage is expressed as a positive number).physical代写