Now that you have some practice using an analog spectrometer from the previous lab, we can now turn our sights on the spectrum of light from the sun! We normally think that sunlight is made up of all the colors of the rainbow, but is that really true? Maybe there are clues in the solar spectrum that can help us understand what that big ball of gas is made of!

By the end of this lab, students will have…

• …learned to use a digital optical spectrometer;
• …revisited some of the spectra collected in the last week to make more accurate measurements of emission wavelength;
• …observed reflected solar light and identified the absorption lines present in the solar spectrum;
• ,,, associated as many lines as possible in the solar spectrum with known emission lines from the individual discharge lamps (or values found elsewhere); and
• …investigated additional contributions to the measured spectrum which are not directly from the sun (such as reflections off glass and/or room sources).

Before we start today's lab, we are asking all students to complete a short (<5 minute) survey in which you will have a chance to provide feedback on your TA. Your answers are anonymous and will not affect your grade in any way. You may access the survey from your personal computer, a lab computer, or your phone.

At the end of the quarter, TAs will receive average scores and comments from their lab section(s).

Do not include any identifying information in your responses. If you have any feedback to provide to which you would like a response, please send it to David McCowan (mccowan@uchicago.edu).

If you cannot or do not want to complete the survey now, you may complete it at home. The survey will remain open until Saturday, March 1 at 5:00 pm.

You have access to all the tools from the last experiment (including the analog spectrometer and different emission lamps), but the TA will introduce you to a new tool – a digital spectrometer. You will look at the solar spectrum using both the analog spectrometer you are familiar with and with this new digital spectrometer, and you will put together the pieces we have been building over the last few labs by identifying the wavelengths of the absorption lines – the so-called Fraunhofer lines – that you will hopefully see. From these lines, can we tell what elements are present in the Sun's atmosphere?

Remember to write down everything you see and do in your group lab notebook.

• Make sketches, do calculations, take notes, and record observations. Your TA may ask to see your notebook during lab, and will read over it afterwards to assign a grade to the group.
• Use the digital group lab report to communicate the process and results from your experiment.

The Google Chrome web app that connects to the digital spectrometer is located at SpectralAnalysis.app. You can access this site from either a lab computer or your own personal laptop. Note that this app does not work in other browsers, but a downloadable version is available here: https://www.vernier.com/product/spectral-analysis/.

Within the app, connect your spectrometer (either through USB or wirelessly through Bluetooth) and then select Select Emissions: vs. wavelength (full spectrum) from the menu.

• If connecting by USB, the spectrometer may show up as “unknown device” in the menu; this is normal.
• If connecting by Bluetooth, make sure the ID on the front of your device matches the device Bluetooth ID.)

Consider: What do you see when you point your analog spectrometer towards the light reflected from the sun? Is it like you expected? Are you able to see any unusual features?

Consider: What do you see when you point your digital spectrometer towards the light reflected from the sun? What new information is available compared to the analog spectrum? What expected or unexpected features do you see?

Consider: When you use your digital spectrometer on the hydrogen emission lamp, what do you see? Compare this with what you observed last lab?

Consider: As you look at other emission spectra, do you find any lines that match up with the Fraunhofer absorption lines? What does that tell us about the sun's atmosphere. (And… while you're thinking about that, what does that tell us about Earth's atmosphere?)

Consider: What do you learn from looking at the spectra of other light sources in the room (like light bulbs or glowing electronics)? How do these spectra compare to what we see from either the emission lamps or the sun?

At the end of the lab, you will need to record your final conclusions (about 1 or 2 paragraphs) in your lab report summing up the important results and take-away points from your experiment. Remember that you should only draw conclusions which are supported by the data, so be ready to back up any statements you make!

When you're finished, save your file as a PDF and upload it to Canvas. (Only one student needs to submit the report, but make sure everyone's name is on it!) If you make a mistake, you can re-submit, but work done after the end of the lab period will not be accepted.