Light lab chm 130

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Central Arizona College *

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130

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Astronomy

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Dec 6, 2023

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Light lab Objectives: Build a spectroscope. Investigate the basic properties of the visible light spectrum using a spectroscope. Observe and relate the wavelengths of different colors of light to positions on the electromagnetic spectrum. Students will use the electromagnetic spectrum to learn how to differentiate between true color and false color images of galaxy and other space photos (also, known as Astronomical images) . What did you do during COVID-19 social distancing time? This wasn’t the first time of social distancing. At age 22, in 1665, Isaac Newton had to leave Cambridge University in England because of the Plague. He spent two years studying independently at home, and developed calculus, the law of gravity, and light laws (optics). At home, Newton saw that a simple glass prism could split (refract) sunlight into all the colors of the rainbow (a spectrum). He was also able to recombine the spectrum of visible colors back into white light, unless he had blocked out some colors in the path of the light. Newton disperses light with a glass prism. APIC/HULTON ARCHIVE/ GETTY IMAGES When Newton started studying light, there were no studies or books where he could read about it, so he tried to describe what he saw, which he at first described as six colors. Anyone with an appropriate glass item and sunlight can see just what he saw. After Newton’s time, everyone else was told what colors Newton thought he saw, so every modern book describes his naming of seven visible colors, which is what he decided to say. When you look at a rainbow or any other spectrum, you might be able to imagine dividing it the way he did, but you also might find it easier to group the shades of light into just six colors, based on the three primary colors and the three blends halfway between them. Human eyes have three types of color-sensing “cones” in them, which roughly correspond to the three primary colors, or to long, medium, and short wavelengths of visible light.

So, why did Newton choose to group the light into seven colors (ROY G. BIV)? He thought that seven was the most perfect mystical number, due to the opinions of the ancient Greeks, the number of unique tones in a musical octave, the number of days in a week, and the number of large objects then known to be visible in our solar system. Of course, in the modern era, people realize that these are not relevant reasons. In 1975, Prof. Isaac Asimov joined other commentators in advocating for everyone to return to the six-color idea. In the 1800s, other scientists discovered infrared and ultraviolet light that human eyes cannot detect and figured out how to measure the wavelengths of specific colors of visible and other light energy, such as radio waves. Part A: Make your own prism to create a rainbow. (Otherwise, known as building your own “spectroscope”) Option 1) Sunlight! When using sunlight to help create the rainbow, the sun needs to be at an angle in the sky (not directly above you). A general suggestion is NOT between 10a.m. and 2p.m. If you have time, try a couple of different times of the day to find what time is optimal to create your own rainbows with glasses of water. Write your name diagonally in the center of a white piece of paper. In an area with sunlight, place the two different sizes or types of glasses (wine glasses and/or medium-to-large drinking glasses with some variations in the glass) - that are partially filled at least ½ to nearly full of water- on that piece of paper. Try with your back to the sun or some other angle to best create the rainbows. You might even need to block a bit of the sun if it is too bright outside. Observe the sunlight stream through the water and create images. Move the glasses until you find the best spot that a rainbow from each glass shows up on the white paper, with the two rainbows ending up somewhere on your name. This will take some experimenting. Take a picture that has your two rainbows touching your name. Option 2- not as easy as an option) Flashlight in a darkened room! Write your name diagonally in the center of a white piece of paper. Using a flashlight (the flashlight can NOT be an LED flashlight as LED flashlights are monochromatic), place two different sizes or types of glasses (wine glasses and/or medium to large drinking glasses with some variations in the glass) of water on a white piece of paper in a

somewhat darkened room. You will need to experiment on what amount of water works best for you (somewhere between ½ to nearly full). Shine a flashlight (or even the flashlight from your phone works well) on the sides of the glasses at a little bit at an angle. Move the flashlight up and down or further from the glasses and then closer until you find the best spot that a rainbow from each glass shows up on the white paper, that has your name between the two rainbows. Take a picture. Question 1. Insert your picture creating the rainbows here. Remember to compress your image. Explain what you needed to do to get your rainbows in just the right angle. Describe your trial and error (and then success) process. Part B: The electromagnetic spectrum Question 2. The following three images are from a NASA science electromagnetic spectrum website. How are they similar? Include what point you think I am trying to make.

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Part B Step 1. Check out the following 5 minute video from the NASA website on the electromagnetic spectrum https://science.nasa.gov/ems/09_visiblelight and then answer the questions below. Use the previous video on visible light to answer the following questions: 1) Why is the sky blue? 2) Why does a sunset have the characteristic red and yellow colors? 3) What is something else of interest that you learned from the video? 4) The next time you are out in the dark looking at the stars, look at the Orion Constellation. Here is a picture of the Orion Constellation to help you: With your naked eye, you should be able to make out a red star ( Betelgeuse) and a bluish- white star (Rigel). What does the color tell us about those two stars? Step 2: Watch the following short 5-minute video about the region of light right after the visible range (ultraviolet). Once you have watched the video, write three questions of your own on that video as if you were the instructor (include the answers). https://science.nasa.gov/ems/10_ultravioletwaves Put your three questions and their answers here:

Part C: Spectroscopy Watch the following two short videos and answer the questions that follow. https://www.khanacademy.org/partner- content/nasa/measuringuniverse/spectroscopy/a/absorptionemission-lines https://www.khanacademy.org/partner- content/nasa/measuringuniverse/spectroscopy/v/spectroscopy-in-action 1. What are emission lines and how they relate to the “finger print signature” of an element? 2. How is spectroscopy used to identify components in space for example, methane on Mars? 3. What purpose is there for putting spectroscopes in the telescopes like Chandra, Spitzer, Hubble, James E Webb? Part D: Space telescope images using different parts of the electromagnetic spectrum There are many examples of space images with "false" colors. "False" colors are when astronomical images are constructed from digital data collected by a variety of electronic sensors outside of the visible spectrum. To create images from data outside of the visible spectrum, it is

necessary to represent it in "false" colors so that we can “visualize” the radiation we can’t see but that exists. This is opposed to Hubble’s pictures which quite often are "true" color images due to them operating in the visible spectrum. The following NASA website gives us an example of image that is a composite – it uses data from different telescopes that measure different wavelengths. https://science.nasa.gov/ems/04_energytoimage Messier 101 galaxy in x-ray, infrared, and visible light. Credit: NASA, ESA, CXC, JPL, Caltech and STScI “This composite image of the spiral galaxy Messier 101 combines views from Spitzer, Hubble, and Chandra space telescopes. The red color shows Spitzer's view in infrared light. It highlights the heat emitted by dust lanes in the galaxy where stars can form. The yellow color is Hubble's view in visible light. Most of this light comes from stars, and they trace the same spiral structure as the dust lanes. The blue color shows Chandra's view in x-ray light. Sources of x-rays include million-degree gas, exploded stars, and material colliding around black holes. Such composite images allow astronomers to compare how features are seen in multiple wavelengths. It's like "seeing" with a camera, night-vision goggles, and x-ray vision all at once.” The following OpenStax links give information about various websites of different telescopes that use different parts of the electromagnetic spectrum to view the stars. There are, also, images of the Flame nebula, Cassiopeia A, and the Helix nebula from Spitzer and a Chandra astronomical image. https://openstax.org/books/astronomy/pages/6-5-observations-outside-earths-atmosphere https://openstax.org/books/astronomy/pages/5-2-the-electromagnetic-spectrum The James E Webb telescope was launched in Dec 2021 and is sending back pictures with even more clarity. Look up “James Webb space telescope images” and pick your favorite image from these.

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Now that you know about the different galaxies’ images NASA has provided for us, and we know they don’t look like that if we view them only with our naked eye, find a favorite astronomical image from NASA that is not from the James E Webb Telescope and one from the James E Webb Telescope. Insert the two images you chose on the last page of this lab on Post Lab question #3 and answer the question on #3. Part E: Fireworks The flame test commonly used in labs is used to see the likely identity of an unknown metal ion based on the characteristic color the salt turns the flame of a Bunsen burner. As with ringing a bell, we’re not using the flame to react the metal atoms, but just to put in energy and see what way that energy comes out. The heat of the flame causes energy to be absorbed by an electron of an atom or molecule, causing it to become excited, but unstable. When the electron returns to a lower energy state the energy is released in the form of a photon (light). The energy of the photon determines its wavelength or color. The characteristic emission spectra can be used to differentiate between some elements. Different metals produce different colors. The different colors we see in fireworks are from the use of different metals in the powders. Watch the following fireworks presentation from the 11:22 minute mark to the 15:45 minute mark to learn the chemistry behind the different colors in fireworks. (If you continue to watch to about the 20-minute mark you will learn many other items about how to get the fireworks to produce certain effects, including the different sounds). Ignore the Dutch subtitles. Then answer the questions below. https://www.youtube.com/watch?v=OaF2XzwN2HM What colors do the following metals produce? 1) Barium 2) Strontium 3) Calcium 4) Sodium 5) Copper 6) Titanium Post lab questions on the following page.

Post lab questions: Using the knowledge you have gained doing this lab, answer the following questions. 1. Draw (or insert a picture of) the complete electromagnetic spectrum and label the sections. 2. Why are astronomical images often labeled as "false" colors? 3. Insert your two favorite “false” color astronomical images here. Include what telescopes took the images and the part of the electromagnetic spectrum each image is measuring. 4. Look up LiDAR. What is it? What parts of the electromagnetic spectrum does it use? Name three applications that LiDAR plays an important role. 5. At Abbott labs here in Casa Grande where they make nutritional supplements, they use the flame test to determine the amount of iron in the baby formula. What color will they see in the flame test for iron? 6. What is your opinion on the colors of the rainbow? Should we leave them at 7 colors as Isaac Newton proposed in the 1600’s, or go with 6 colors as Isaac Asimov proposed in 1975? Explain your reasoning.

Light lab chm 130

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