interference and diffraction

For each lab this semester you will be given an online simulation to perform that week’s lab in place of performing the lab with physical equipment.

Due to the nature of these simulations, corrections and additions will be made each week to your lab as it exists in your lab manual.   Pay close attention to these instructions as you will be graded on these additions.  All existing questions in the lab manual should be answered unless specified otherwise.

This week you will work individually to write a Formal Report.  All work on this week’s lab should be done individually and no collaboration with your group or other students is permitted.  A .pdf submission per student is needed in HuskyCT.

In addition to the Pre-lab, data collection from the simulation should be completed individually before attending your lab session.  All students must still attend their lab session to receive information from their TA about this lab.

Formal Report Deadlines

• Draft (optional)
  • You may write an optional draft of your formal report to receive feedback from your TA. This is due one week after your synchronous lab session at the lab start time.  For example, if your synchronous lab session for Ohm’s Law takes place on Monday at 9:00AM, your draft would be due the following Monday at 9:00AM.  Drafts must be complete and are not accepted late.
• Final Submission
  • If you did not submit a draft:
    • Two weeks after your synchronous lab session at the lab start time. Using the same example as above- if your lab session occurs Monday at 9:00AM, your final submission of the formal report would be due two weeks later Monday at 9:00AM.
  • If you submitted a draft:
    • Final submission of the formal report is due either three days after receiving TA feedback on your draft or two weeks after your synchronous lab session at the lab start time, whichever occurs later in time.

 

 

Lab: Interference and Diffraction

11.1 Pre-lab

Link to Pre-lab simulation:  https://phet.colorado.edu/sims/html/wave-interference/latest/wave-interference_en.html

[11.1] Go to the “Waves,” section of the simulation.  Complete as written.

[11.2] Go to the “Slits,” section of the simulation.  Select the laser pointer icon from the menu on the right side to change from water to light.  Complete as written.

11.2 Introduction

Complete as written

11.3 Apparatus

In place of the physical apparatus described in this section, you will be using the following digital simulation to replicate the experiment:

https://phet.colorado.edu/sims/html/wave-interference/latest/wave-interference_en.html

You will be using again the “Slits,” section of this simulation and the “light,” waves by using the laser pointer icon.  These settings will remain the same for the rest of the lab.

11.4 Theory

Complete as written

11.5 Experiment

[11.11] Omit.  Instead, complete the following:

First, make sure you are in the “Slits,” section of the simulation, and you have the laser pointer selected.   Check the boxes for “Screen,” and “Intensity.”  These settings should remain constant for the entire experiment.

Single Slit

1. Choose, “One Slit,” from the drop-down menu on the right.
2. Leave the slit (yellow bar in the center of the simulation) at its default distance from the screen. Keep this constant.
3. Using the Frequency slider on the righthand side, choose any frequency of light to be used for this experiment. Take note of your chosen color.  This should remain constant for the entire experiment.
4. Use the “Slit Width,” slider to set the slit width to 200nm.
5. Click the green button on your light source and click play on the simulation. You will see a curve appear on the “Intensity,” graph.
6. Using the measuring tape from the top of the right-hand side menu, measure the distance “L,” between your slit and the screen.
7. Using the same measuring tape, measure the distance y as shown in figure 10.1. This is the distance from the maximum of your curve to the minimum of that curve.  The maximum will always appear at the center of this graph, and the minimum is the point at which the curve reaches zero.  You may need to zoom in or out on the intensity display using the magnifying glass buttons to view these maxima and minima points.  Record this value.
8. Repeat steps 3-7 for multiple values of single slit width. It is up to you to choose which data points to collect, and how many to measure.  Think about what makes a good data set based on our previous experiments this semester.

Double Slit

1. Choose, “Two Slits,” from the drop-down menu on the right.
2. Keep your distance, L, between the slits and the screen the same as above. Keep the chosen frequency of light the same as you used above.
3. Use the “Slit Separation,” slider to set the slit separation to 800nm.
4. Use the “Slit Width,” slider to set the slit width to 200nm.
5. Click the green button on your light source and click play on the simulation. You will see a curve appear on the “Intensity,” graph.
6. Using the same measuring tape, now measure the distance y as shown in figure 10.2. This is the distance between maxima of your curve.  You may need to zoom in or out on the Intensity display to take these measurements.  Record this value.
7. Keeping the slit separation constant, repeat steps 4-6 for one additional different value of slit width.
8. Repeat steps 3-7 for multiple values of slit separation. It is up to you to choose which data points to collect, and how many to measure.  Think about what makes a good data set based on our previous experiments this semester.
9. You should have a collection of data points for a variety of slit separations. For each chosen slit separation, you should also have two different measurements for slit width.

[11.12] Complete as written

11.6 Analysis

For your data set, use the equations you developed in the theory section to calculate the wavelength from your measured values for each part of the experiment.  Use your resources to find the color of light that corresponds to each calculated wavelength.  Does this match the color of light chosen by each group member in the simulation?  If not, discuss any possible sources of error or limitations of the experiment that may have contributed to this discrepancy.

[11.13]-[11.17]- Complete as written

11.7 Conclusion

Complete as written