Spectrum and Telescope Labs(1)

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William Rainey Harper College *

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AST-112

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Astronomy

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Apr 3, 2024

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SPECTRUM LAB Name_______America Santos_________________________ Date_________________ MATERIALS Spectrometer, 1 Incandescent light bulb (bulb with a glowing filament), pencil or pen (an object with a dull point), 1 fluorescent light, colored pencils or pens, white surface, such as a movie screen or wall. PROCEDURE 1. At the back of the room you will notice several spectrometer stations. These will include an incandescent light, a fluorescent light, and several gas tubes that will contain H, He, Ar, Ne, and/or other gases. Viewing through each spectrometer, you will notice a variety of spectra (continuous, emission, combination of the two) depending on the light source you are viewing. Do not touch the spectrometers as the alignment will be thrown off. You should see the scale similar to that illustrated below. You should also notice colors at various places inside the spectrometer. This is caused by light entering. the spectrometer from different sources. 2. Set the power setting to low, but bright enough so that the bulb still glows and is easily visible. Look at an illuminated incandescent bulb through the spectrometer. You should see a continuous spectrum of colors from red through violet. On the scale below (Station 1), draw the colors you see. Use colored pencils to shade in the observed colors. The various colors are described by wavelength in nanometers (nm) or by the energy of the photon, expressed in electron-Volts (eV). Note: 1 eV = 1.6022 x 10 -19 joule. Station 1 Incandescent light (Low power): Roger Kolman, PhD Rev KPage 2/17/19 BLUE GREEN RED

3. Read the number on the scale corresponding to the light farthest to the right that you can see and the number corresponding to the light farthest to the left that you can see. a) The observed spectrum extends from ______________nm to __________________ nm. b) The colors at these places on the scale are: _____________ and_______________. c) Which color(s) appear the brightest?___________________________ 4. Now set the power on the incandescent bulb to a high-power setting and observe the bulb through the spectrometer. How did the spectrum change on the high setting compared with the lower power setting? Which color spears the brightest on the high-power setting? 5. Now, proceed to Station 2 and look at the fluorescent light through the spectrometer, and record what you see on the scale below. Note: In addition to the full spectra, you should all see several weak vertical spectra. Record these as well. Station 2 Fluorescent light : The spectrum extends from ________________nm to __________________________nm. 6. Describe the spectrum you see. Is it different from the spectrum you observed at Station 1? . 7. Read the positions of the bright lines on the scale and record them in Table 1. Table 1 Color Position Roger Kolman, PhD Rev KPage 2/17/19

8. Now you are going to look at 3 spectral tubes that will include H and other gases. Draw the spectrum you observe in the diagrams for each tube. Also, record the color and wavelength of each spectrum you observe in the accompanying tables. After you have observed the gas, refer to the spectral line chart in the lab and attempt to determine the identity of each gas. Tube 1 ______________ Type of Gas?_______________________ Color Position Tube 2 __________________ Type of Gas? _______________________ Color Position Roger Kolman, PhD Rev KPage 2/17/19

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Tube 3 __________________ Type of Gas?_______________________ Color Position Tube 4 ______________________ Type of Gas?_______________________ Color Position 9. What were the major differences between the spectra of the incandescent bulb and the spectra of the gas tubes? Roger Kolman, PhD Rev KPage 2/17/19

10. Was the spectrum of the fluorescent bulb closer to the incandescent bulb or the gas tubes (in general, not a specific one)? Explain your reasoning. Roger Kolman, PhD Rev KPage 2/17/19

AST112/115 TELESCOPE LAB Name___________________________ Date _________________ Section ______________ Purpose To identify the parts, functions, magnification, and light gathering power of the refracting and reflecting telescope and learn how to operate a telescope in the classroom. Procedure 1. The refracting telescope: Below is an example of a refracting telescope and an illustration of the light path through the objective lens and the eyepiece. Roger Kolman, PhD Rev KPage 2/17/19 Focal Point

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Roger Kolman, PhD Rev KPage 2/17/19

2. Give the function for each part labeled: Part Function Objective Lens Eyepiece Focus Knob Tube Viewfinder Fine-Adjustment Knobs Polar Axis Declination Axis 3. Draw a schematic of the telescope and show the path that light takes, from the objective lens to your eye. Roger Kolman, PhD Rev KPage 2/17/19

4. The magnification of the telescope: a. What is the focal length ( f obj ) of the objective lens of the telescope? b. What is the focal length ( f eye ) of the eyepiece of the telescope? c. What is the magnification of this telescope using this eyepiece? NOTE: This is a ratio and hence will have no units as they will cancel out!!! magnification = f obj / f eye = d. What would be the magnification of the refracting telescope if you used an eyepiece with f eye = 10 mm? magnification = e. In words, summarize how we determine the magnification of a telescope. Roger Kolman, PhD Rev KPage 2/17/19

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5. The reflecting telescope: Label the parts: main mirror, secondary mirror, eyepiece, focus knob, telescope tube, viewfinder, declination and right ascension fine-adjustment knobs, declination, and right ascension lock levers. Roger Kolman, PhD Rev KPage 2/17/19 Focal Point

6. Give the function for each part labeled: Part Function Main Mirror Secondary Mirror Eyepiece Focus Knob Tube Viewfinder Fine-Adjustment Knobs Polar Axis Declination Axis 7. Draw a schematic of the telescope and show the path that light takes, from the main mirror to your eye. 8. The magnification of the telescope: a. What is the focal length ( f obj ) of the main mirror of the telescope? b. What is the focal length ( f eye ) of the eyepiece of the telescope? Roger Kolman, PhD Rev KPage 2/17/19

c. What is the magnification of this telescope using this eyepiece? magnification = f obj / f eye = d. What would be the magnification of the refracting telescope if you used an eyepiece with f eye = 10 mm? magnification = e. In words, summarize how we determine the magnification of a telescope. 9. How does the light gathering power of the telescope compare to that of the Keck telescopes? To do this exercise you will need to measure or find the diameter of the objective lens of each telescope and then ratio the squares of the two diameters, since the area of a circle depends on the radius squared (since we are taking a ratio, the "2" in "2*radius = diameter" cancels). Example: D 1 = 10 cm, D 2 = 200 cm Ratio = 200 2 /10 2 = 400. That is, the larger telescope is 20 times as large, but has 400 times the light gathering power. The 10-meter Keck telescope in Hawaii is one of the largest in the world. Compare its light gathering power to our telescope (make sure you use the same units for all quantities) -- Roger Kolman, PhD Rev KPage 2/17/19

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Spectrum and Telescope Labs(1)

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