AP Physics 2 Unit 10 Lab

Elisa Alvarado, Sarah Cratem, Ryan Partain, Julia Reidy

Mr. Thomas

AP Physics 2 cmod

14 March 2016

Unit 10: Quantum Model Lab Report

Objective: To determine the relationship between brightness and density of light related to the current it produces.

Apparatus:

Procedure:

Finding the Relationship Between Current and Photon Density
1. Choose Sodium as the target metal
2. Set the voltage to a constant 1 V
3. Set the wavelength to 250 nm
4. Set the photon density = 0.01
5. Hit “Record Data Point”
6. Change the photon density by adding 0.10. Hit “Record Data Point”
7. Repeat step 6 for (0.10,1.00]; you should have 11 data points

Finding the Relationship between Current and a Change in Potential
1. Using Sodium, set the photon density = 1
2. Set the wavelength at 250 nm
3. Set the voltage = 0 V
4. Hit “Record Data Point”
5. Change the voltage by adding 0.500V. Hit “Record Data Point”
6. Repeat Step 5 for (0.500V, 5.000V]; you should have 11 data points

Finding the Relationship between Maximum Kinetic Energy and Frequency
1. Using Sodium, set the photon density = 1, and set the voltage = 1 V
2. Start with wavelength = 800 nm; this will result in a frequency of 3.75 x1014Hz
3. Hit “Record Data Point”
4. Subtract 86 nm from the wavelength to increase the frequency. Hit “Record Data Point”
5. Repeat Step 4 for [200 nm, 700 nm)
6. Calculate by using a spreadsheet software and the equation 𝜙 (multiply Plank’s constant, eV·s, by the frequency column and subtract the work function for Sodium which equals 2.28eV)

Data Table:

Graphs:

Energy vs. Frequency

Conclusion:

In the first trial the independent variable was photon density and the dependent variable was current. In the second trial the independent variable was voltage and dependent was current. In the third trial the independent variable was wavelength/frequency and the dependent was Kinetic Energy, which was solved for using the equation UK = (4.063 x 10-15eVs)(f) - 2.828eV, where Planck's constant is equal to the slope. The x intercept shows the minimum amount of frequency needed to expel an electron from the Sodium. The y intercept shows us how much force is needed to eject an electron from the Sodium. The generalized equation we can derive from this data is E= hf - ϕ. The slope (h) represents Planck's constant.  The equation E= hf - ϕ shows that kinetic energy of the photoelectron is equal to Planck's constant (h) multiplied by the light’s frequency minus the y intercept (ϕ). The errors that could have happened during our experiment are limited because we used a computer to compute the data used in our analysis. The only way for error to be possible is if we rounded numbers wrong or if we accidentally plugged numbers wrong into our calculator.