DOCSLIB.ORG

Indigo Blue EXPERIMENT: VISIBLE LIGHT SPECTROSCOPY in This

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Indigo Blue EXPERIMENT: VISIBLE LIGHT SPECTROSCOPY in This EXPERIMENT: VISIBLE LIGHT SPECTROSCOPY In this experiment we will be investigating the color produced when light is absorbed by a transparent solution. The color a solution will appear to us can be predicted by using the color wheel. If the chemicals in the solution absorb only red light, the solution will appear blue-green. Blue-green is the color directly opposite red on the color wheel. Colors opposite one another on the color wheel are called complementary colors. Red and blue-green are complementary colors. If a solution appears blue then we would find that the chemicals are absorbing orange light since blue and orange are complementary. It should be noted that there is no such thing as purple light (purple is red + violet ) so if a solution is green it can’t absorb “purple” light. Instead it absorbs reds and violets. Indigo Blue We would also expect that as the concentration of the absorbing chemicals increase the amount of light absorbed would probably increase also. This relationship is called “Beer’s Law.” The instrument we will use to determine the type of light absorbed by the solution and the amount of light absorbed is called a spectrometer. Verification of the Color Wheel Connect the spectrometer to the USB port of your computer and open Logger Pro. You should see this screen: Select Experiment from the toolbar and then Calibrate, Spectrometer from the menu. Fill a sample holder (called a cuvette) about 3/4 full of distilled water and position it into the spectrometer so that the rubbed sides of the cuvette do not interfere with the light beam. To avoid having fingerprints interfere with the light readings, always handle the cuvettes near the top. The special Kimwipe tissues can be used to wipe the outside of the cuvettes. After the instrument lamp has finished warming up, click Finish Calibration and wait until the spectrum calibrates throughout the wavelength range. When completed click OK You will observe the absorption spectrum of 3 solutions: blue food coloring, yellow food coloring, and phenolphthalein in a basic solution. Fill another cuvette about 3/4 full of blue food coloring. Place the cuvette containing the solution into the spectrometer and press the green Collect button in toolbar. The button turns red. Your spectrum might look something like the one below. Press Stop to terminate the run. Logger Pro is plotting absorbance along the Y axis and wavelength along the X axis. Absorbance is a variable that measures the amount of light the solution absorbs. The greater the absorbance, the more light of that particular wavelength the solution is absorbing. To measure the spectrum of the next solution store your current trial by selecting Experiment from the toolbar and then Store Latest Run. Remove the cuvette and replace it with one containing yellow food coloring, press the green Collect button, then Stop, and Store the Latest Run. You will notice that once you have recorded the second solution, both graphs appear. In the same way, measure the spectrum of phenolphthalein in basic solution. You will now have a graph that displays the spectra for three compounds. The relative heights of your peaks may be different from that shown in the sample graph since the concentrations of the solutions may be different from the ones used to make the sample. Save your file to your computer and transfer the file to your lab partner at this point. Each person needs to complete his/her own graph modifications. The Effect of Concentration on the Spectrum You will measure the spectrum of distilled water and of four solutions of crystal violet. One solution will have been prepared for you and the concentration will be on the stock bottles. The three diluted solutions of crystal violet you will prepare. To prepare the diluted solutions, use pipets to add the quantities of solution shown in the table below to initially dry 50 mL beakers. Stir the solutions thoroughly. Assume that the volumes are additive and in your Excel file, calculate the molarity of crystal violet in each diluted solution. You now have 5 solutions: distilled water plus 4 solutions of crystal violet. volume of crystal violet (mL) volume of water (mL) 10.00 5.00 10.00 10.00 5.00 10.00 Close your previous Logger Pro file and open a new one. Since this part of the experiment is more quantitative than the first part of the experiment you want to be careful how the cuvettes are placed into the spectrometer. The cuvette holder in the spectrometer is a little too large for the cuvettes (poor design) so that the cuvette can be rotated slightly in the holder. When you are positioning the cuvettes for this part of the experiment try to place them into the holder in as exactly the same position as you can. You will also see a small ink dot on the top edge of the cuvette. This is a reference mark that will allow to place the cuvette into the sample holder so that the same side of the cuvette is facing the lamp for each trial. Calibrate the spectrometer with distilled water as you did in the first part of the experiment and record the spectrum of the distilled water. Pour out the distilled water and rinse the cuvette with a few small portions of one of the crystal violet solutions. Be careful that you don’t use so much that you don’t have enough to fill the cuvette. Once rinsed with solution, fill the cuvette with solution, wipe the cuvette with a tissue, place the cuvette into the sample holder with the same orientation of the reference mark, and record the spectrum. Pour out the crystal violet solution and rinse the cuvette with distilled water. To make sure all the crystal violet has been removed, rinse the cuvette with a small amount of 1 M HCl. The acid will remove any crystal violet that has stained the cuvette. Thoroughly rinse the cuvette with distilled water to remove all the acid. Then rinse and fill the cuvette with the next crystal violet solution. Dry off the cuvette and record the spectrum. Repeat this process of rinsing and filling until you have recorded the spectra for distilled water and the four crystal violet solutions. When you are finished your graph will look something like this: Save the file to your computer and transfer the file to your lab partner at this point. Each person will work on his/her own computer after this point. You can now unplug the spectrometer from your computer. Lab Report: 1. Open up the Logger Pro file from the first part of the experiment. 2. Although you many remember (at least today) which line corresponds to a given substance, another person viewing the graph will not know. Whenever more than one line appears on a graph we need a legend to identify which each line represents. To do this, right click on the graph and select Graph Options. Click on the Legend and the Point Protectors. To improve the cosmetics, click off the Mouse Position and Delta and change the Major Tick Style to No Line. A legend box is now displayed on the graph that matches the color of the line and the shape of the point protectors to a particular trial. Since Run 1 has no meaning to an observer we need to label the trials with the names of the substances used. Use the arrows at the bottom of the data table to scroll across until Run 1 is visible. Double click on “Run 1" in the column heading and change the name of from Run 1 to the name of the substance used in the first trial...blue food coloring. The graph now looks like this: In a similar way change the names of Run 2 and Run 3 to represent the substances used. You can expand the data table view by dragging the edge of data table. When finished your graph should look something like this: If it bothers you that the graph for blue food coloring is displayed in red and the yellow food coloring is in blue you can change the displayed colors to anything you would like. Double click on the Abs column heading in the data table, select Options and you can change the color as well as the size and shape of the point protectors to anything you would like. 3. Graphs should always have a title. To do this right click on the graph and select Graph Options. The title is usually written (name of Y variable) vs (name of X variable) with any additional words necessary to add clarity. In this case the title would be Absorbance vs Wavelength plus whatever else you might want to add for clarity. 4. Often you need to change the scale on the graph so that the graph fills the greatest area of the screen possible. Right click on the graph and under Autoscale select the type of autoscaling you want depending on whether or not you want to see the origin in the graph. Since the X axis begins with 400 nm, choose Autoscale (not Autoscale from 0). This should scale the Y axis so that the peak absorbance if near the top of the graph. 5. Move the legend box as necessary so that it does not cover up any of the lines and copy the graph to your Excel file. To copy the graph, right click on the graph and select copy. If your computer is a Mac, when the graph is copied, the colored background is retained.
Load more

Recommended publications
  • WHITE LIGHT and COLORED LIGHT Grades K–5
    WHITE LIGHT AND COLORED LIGHT grades K–5 Objective This activity offers two simple ways to demonstrate that white light is made of different colors of light mixed together. The first uses special glasses to reveal the colors that make up white light. The second involves spinning a colorful top to blend different colors into white. Together, these activities can be thought of as taking white light apart and putting it back together again. Introduction The Sun, the stars, and a light bulb are all sources of “white” light. But what is white light? What we see as white light is actually a combination of all visible colors of light mixed together. Astronomers spread starlight into a rainbow or spectrum to study the specific colors of light it contains. The colors hidden in white starlight can reveal what the star is made of and how hot it is. The tool astronomers use to spread light into a spectrum is called a spectroscope. But many things, such as glass prisms and water droplets, can also separate white light into a rainbow of colors. After it rains, there are often lots of water droplets in the air. White sunlight passing through these droplets is spread apart into its component colors, creating a rainbow. In this activity, you will view the rainbow of colors contained in white light by using a pair of “Rainbow Glasses” that separate white light into a spectrum. ! SAFETY NOTE These glasses do NOT protect your eyes from the Sun. NEVER LOOK AT THE SUN! Background Reading for Educators Light: Its Secrets Revealed, available at http://www.amnh.org/education/resources/rfl/pdf/du_x01_light.pdf Developed with the generous support of The Charles Hayden Foundation WHITE LIGHT AND COLORED LIGHT Materials Rainbow Glasses Possible white light sources: (paper glasses containing a Incandescent light bulb diffraction grating).
    [Show full text]
  • Absorption of Light Energy Light, Energy, and Electron Structure SCIENTIFIC
    Absorption of Light Energy Light, Energy, and Electron Structure SCIENTIFIC Introduction Why does the color of a copper chloride solution appear blue? As the white light hits the paint, which colors does the solution absorb and which colors does it transmit? In this activity students will observe the basic principles of absorption spectroscopy based on absorbance and transmittance of visible light. Concepts • Spectroscopy • Visible light spectrum • Absorbance and transmittance • Quantized electron energy levels Background The visible light spectrum (380−750 nm) is the light we are able to see. This spectrum is often referred to as “ROY G BIV” as a mnemonic device for the order of colors it produces. Violet has the shortest wavelength (about 400 nm) and red has the longest wavelength (about 650–700 nm). Many common chemical solutions can be used as filters to demonstrate the principles of absorption and transmittance of visible light in the electromagnetic spectrum. For example, copper(II) chloride (blue), ammonium dichromate (orange), iron(III) chloride (yellow), and potassium permanganate (red) are all different colors because they absorb different wave- lengths of visible light. In this demonstration, students will observe the principles of absorption spectroscopy using a variety of different colored solutions. Food coloring will be substituted for the orange and yellow chemical solutions mentioned above. Rare earth metal solutions, erbium and praseodymium chloride, will be used to illustrate line absorption spectra. Materials Copper(II) chloride solution, 1 M, 85 mL Diffraction grating, holographic, 14 cm × 14 cm Erbium chloride solution, 0.1 M, 50 mL Microchemistry solution bottle, 50 mL, 6 Potassium permanganate solution (KMnO4), 0.001 M, 275 mL Overhead projector and screen Praseodymium chloride solution, 0.1 M, 50 mL Red food dye Water, deionized Stir rod, glass Beaker, 250-mL Tape Black construction paper, 12 × 18, 2 sheets Yellow food dye Colored pencils Safety Precautions Copper(II) chloride solution is toxic by ingestion and inhalation.
    [Show full text]
  • Color Wheel Page 1 Crayons Or Markers Color
    Crayons or markers Color Wheel Cut-out (at the end of this description) String, about 3 feet Scissors Step 1 Color each wedge of the circle with a different rainbow color. Use heavy paper or a paper plate. Step 2 Cut out the circle, as well as the center holes (you can use a sharp pencil to poke through, too!). Step 3 Feed the string through the holes and tie the ends together. Step 4 Pick up the string, one side of the loop in each hand so the circle is in the middle. Wind the string by rotating it, in a “jump-rope”-like motion. The string should be a little loose with the circle pulling it down in the middle. Step 5 Move your hands out to pull the string tight to get the wheel spinning. When the string is fully unwound, move your hands closer together so it can wind in the other direction If it’s not spinning fast enough, keep winding! Step 6 As it spins, what happens to the colors? What do you notice? Color Wheel Page 1 What did you notice when you spun the wheel? You may have seen the colors seem to disappear! Where did they go? Let’s think about light and color, starting with the sun. The light that comes from the sun is actually made up of all different colors on the light spectrum. When light hits a surface, some of the colors are absorbed and some are reflected. We only see the colors that are reflected back.
    [Show full text]
  • C-316: a Guide to Color
    COLLEGE OF AGRICULTURAL, CONSUMER AND ENVIRONMENTAL SCIENCES A Guide to Color Revised by Jennah McKinley1 aces.nmsu.edu/pubs • Cooperative Extension Service • Guide C-316 The College of Agricultural, Consumer and Environmental Sciences is an engine for economic and community development in New Figure 1. Sample color wheel. Mexico, improving the lives of New Color is one of the most important stimuli in the world. It affects our moods and personal characteristics. We speak of blue Mondays, being Mexicans through in the pink, seeing red, and everything coming up roses. Webster de- fines color as the sensation resulting from stimulating the eye’s retina with light waves of certain wavelengths. Those sensations have been academic, research, given names such as red, green, and purple. Color communicates. It tells others about you. What determines and extension your choice of colors in your clothing? In your home? In your office? In your car? Your selection of color is influenced by age, personality, programs. experiences, the occasion, the effect of light, size, texture, and a variety of other factors. Some people have misconceptions about color. They may feel cer- tain colors should never be used together, certain colors are always unflattering, or certain colors indicate a person’s character. These ideas will limit their enjoyment of color and can cause them a great deal of frustration in life. To get a better understanding of color, look at na- ture. Consider these facts: All About Discovery!TM • The prettiest gardens have a wide variety of reds, oranges, pinks, New Mexico State University violets, purples, and yellows all mixed together.
    [Show full text]
  • OSHER Color 2021
    OSHER Color 2021 Presentation 1 Mysteries of Color Color Foundation Q: Why is color? A: Color is a perception that arises from the responses of our visual systems to light in the environment. We probably have evolved with color vision to help us in finding good food and healthy mates. One of the fundamental truths about color that's important to understand is that color is something we humans impose on the world. The world isn't colored; we just see it that way. A reasonable working definition of color is that it's our human response to different wavelengths of light. The color isn't really in the light: We create the color as a response to that light Remember: The different wavelengths of light aren't really colored; they're simply waves of electromagnetic energy with a known length and a known amount of energy. OSHER Color 2021 It's our perceptual system that gives them the attribute of color. Our eyes contain two types of sensors -- rods and cones -- that are sensitive to light. The rods are essentially monochromatic, they contribute to peripheral vision and allow us to see in relatively dark conditions, but they don't contribute to color vision. (You've probably noticed that on a dark night, even though you can see shapes and movement, you see very little color.) The sensation of color comes from the second set of photoreceptors in our eyes -- the cones. We have 3 different types of cones cones are sensitive to light of long wavelength, medium wavelength, and short wavelength.
    [Show full text]
  • Light and the Electromagnetic Spectrum
    © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION © JonesLight & Bartlett and Learning, LLCthe © Jones & Bartlett Learning, LLC NOTElectromagnetic FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION4 Spectrum © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEJ AMESOR DISTRIBUTIONCLERK MAXWELL WAS BORN IN EDINBURGH, SCOTLANDNOT FOR IN 1831. SALE His ORgenius DISTRIBUTION was ap- The Milky Way seen parent early in his life, for at the age of 14 years, he published a paper in the at 10 wavelengths of Proceedings of the Royal Society of Edinburgh. One of his first major achievements the electromagnetic was the explanation for the rings of Saturn, in which he showed that they con- spectrum. Courtesy of Astrophysics Data Facility sist of small particles in orbit around the planet. In the 1860s, Maxwell began at the NASA Goddard a study of electricity© Jones and & magnetismBartlett Learning, and discovered LLC that it should be possible© Jones Space & Bartlett Flight Center. Learning, LLC to produce aNOT wave FORthat combines SALE OR electrical DISTRIBUTION and magnetic effects, a so-calledNOT FOR SALE OR DISTRIBUTION electromagnetic wave.
    [Show full text]
  • Spin the Color Wheel Simple STEM Activities You Can Do at Home
    Spin the Color Wheel Simple STEM Activities You Can Do at Home Purpose: The purpose of this activity is to investigate how colors interact with each other as they more quickly in a circular motion. Standard: S4P1. Obtain, evaluate, and communicate information about the nature of light and how light interacts with objects. a. Plan and carry out investigations to observe and record how light interacts with various materials to classify them as opaque, transparent, or translucent. b. Plan and carry out investigations to describe the path light travels from a light source to a mirror and how it is reflected by the mirror using different angles. S8P4. Obtain, evaluate, and communicate information to support the claim that electromagnetic (light) waves behave differently than mechanical waves. d. Develop and use a model to compare and contrast how light and sound waves are reflected, refracted, absorbed, diffracted or transmitted through various materials. (Clarification statement: Include echo and how color is seen) Materials: Cardboard, string, pencil, colored pencils, markers, or crayons, scissors, glue, ruler, large cup. Procedures: 1. On a piece of paper, trace the mouth of the cup with a pen or pencil. 2. Use a ruler and pencil to divide the circle into 6 even sections. 3. Color each of the 6 sections red, orange, yellow, green, blue, and violet. 4. Cut out the circle and glue the colored circle and cardboard together. 5. Cut the circle out from the cardboard. 6. With adult help, poke two small holes through the wheel near the center of the circle. 7. Feed the string through both holes and tie the ends together like a necklace.
    [Show full text]
  • Middle School Science Experiment Color Theory
    Middle School Science Experiment Color Theory The human eye distinguishes colors using light sensitive cells in the retina. These sensors are rods and cones. The rods give us our night vision and can function in low intensities of light, but cannot distinguish color. The cones let us see color and can resolve sharp images. The light we see, such as the light from the sun, is made up of a mixture of several colors. You will learn more about light as well as about primary and secondary colors in this experiment. Objectives In this experiment, you will: m Gain an understanding of primary and secondary colors m Learn about how a mixture of colors makes up white light m Experiment with the mixing of paint that uses pigments, not light m Take pictures of various colors and compare them when they are mixed and separated Materials m Power Macintosh G3 or better m ProScope Digital USB Microscope and software m Red, blue, and green cellophane or plastic filters m Three flashlights m Red, yellow, and blue watercolor paint m Paintbrush m Water Procedure The first activities involve light and primary colors: 1 Cover one flashlight with red cellophane, one with blue cellophane, and one with green cellophane. (You can use red, blue, and green plastic filters instead of the cellophane.) Darken the room and set up the ProScope USB microscope on the tripod pointing at a piece of white unlined paper. 2 Shine the green flashlight at the white paper. Take a picture of this image using the m0W lens.
    [Show full text]
  • 10 Comparing Colors LABORATORY 1 C L a S S S E S S I O N
    10 Comparing Colors LABORATORY 1 CLASS SESSION ACTIVITY OVERVIEW NGSS RATIONALE In this activity, students first learn that visible light can be separated into different colors. Students then conduct an investigation to collect evidence that indicates that different colors of light carry different amounts of energy. From the results of their investigation, students conclude that higher frequencies of light carry more energy. In their final analysis, students apply the practice of analyzing and inter- preting data as they examine light transmission graphs for three different sunglass lenses. It is through this analysis that students engage with the crosscutting con- cept of structure and function as they determine which sunglass lens provides the best protection for the eyes. NGSS CORRELATION Disciplinary Core Ideas PS-4.B Wave Properties: When light shines on an object, it is reflected, absorbed, or transmitted through the object, depending on the object’s material and the frequency (color) of the light. PS-4.B Wave Properties: A wave model of light is useful for explaining brightness, color, and the frequency-dependent bending of light at a surface between media. Science and Engineering Practices Planning and Carrying Out Investigations: Conduct an investigation to produce data to serve as the basis for evidence that meets the goals of an investigation. Crosscutting Concepts Structure and Function: Structures can be designed to serve particular functions by taking into account properties of different materials, and how materials can be shaped and used. WAVES 3 ACTIVITY 10 COMPARING COLORS Common Core State Standards—ELA/Literacy RST.6-8.3 Follow precisely a multi-step procedure when carrying out experiments, taking measurements, or performing technical tasks.
    [Show full text]
  • Why Is the Sky Purple?
    A laboratory experiment from the Why is Little Shop of Physics at Colorado State University the sky CMMAP purple? Reach for the sky. Overview Necessary materials: Of course, you expect the question to be “why is the sky blue?” That’s the classic version. • 1 “sunset egg” • A white light flashlight And here’s the classic answer: scattering. We’ll talk about what this word means and how it leads to sky color, but we will also see that the The most crucial piece for this experiment is the light from the sky actually contains a bit more “sunset egg.” The small-scale structure of these violet than it does blue! So why do we see glori- glass “eggs” works well to demonstrate the differ- ous blue skies rather than a purple firmament ential scattering that leads to the color of the sky when we gaze up into Earth’s atmosphere? and the color of the sunset. Theory You can find them at rock and nature shops, or you can purchase them in bulk from Pelham Grayson The first person to correctly work out the de- (www.pelhamgrayson.com) under “Magic Feng tails of the process that gives rise to the color of Shui Eggs”. the sky was the English physicist, Lord John Rayleigh, working in the late 1800’s. Rayleigh correctly surmised that the blue color of the sky was a result of scattering. As light enters our atmosphere on its journey from the sun, it interacts with air molecules and is redirected. This redirection is more pronounced for shorter wavelengths toward the blue, or violet, end of the spectrum.
    [Show full text]
  • PRECISE COLOR COMMUNICATION COLOR CONTROL from PERCEPTION to INSTRUMENTATION Knowing Color
    PRECISE COLOR COMMUNICATION COLOR CONTROL FROM PERCEPTION TO INSTRUMENTATION Knowing color. Knowing by color. In any environment, color attracts attention. An infinite number of colors surround us in our everyday lives. We all take color pretty much for granted, but it has a wide range of roles in our daily lives: not only does it influence our tastes in food and other purchases, the color of a person’s face can also tell us about that person’s health. Even though colors affect us so much and their importance continues to grow, our knowledge of color and its control is often insufficient, leading to a variety of problems in deciding product color or in business transactions involving color. Since judgement is often performed according to a person’s impression or experience, it is impossible for everyone to visually control color accurately using common, uniform standards. Is there a way in which we can express a given color* accurately, describe that color to another person, and have that person correctly reproduce the color we perceive? How can color communication between all fields of industry and study be performed smoothly? Clearly, we need more information and knowledge about color. *In this booklet, color will be used as referring to the color of an object. Contents PART I Why does an apple look red? ········································································································4 Human beings can perceive specific wavelengths as colors. ························································6 What color is this apple ? ··············································································································8 Two red balls. How would you describe the differences between their colors to someone? ·······0 Hue. Lightness. Saturation. The world of color is a mixture of these three attributes.
    [Show full text]
  • The Electromagnetic Spectrum CESAR’S Booklet
    The electromagnetic spectrum CESAR’s Booklet The electromagnetic spectrum The colours of light You have surely seen a rainbow, and you are probably familiar with the explanation to this phenomenon: In very basic terms, sunlight is refracted as it gets through water droplets suspended in the Earth’s atmosphere. Because white light is a mixture of six (or seven) different colours, and each colour is refracted a different angle, the result is that the colours get arranged in a given order, from violet to red through blue, green, yellow and orange. We can get the same effect in a laboratory by letting light go through a prism, as shown in Figure 1. This arrangement of colours is what we call a spectrum. Figure 1: White light passing through a prism creates a rainbow. (Credit: physics.stackexchange.com) Yet the spectrum of light is not only made of the colours we see with our eyes. There are other colours that are invisible, although they can be detected with the appropriate devices. Beyond the violet, we have ultraviolet, X-rays and gamma rays. On the other extreme, beyond the red, we have infrared and radio. Although we cannot see them, we are familiar with these other types of light: for example, we use radio waves to transmit music from one station to our car receiver, ultraviolet light from the Sun makes our skin get tanned, X-rays are used by radiography machines to check if we have a broken bone, or we change channel in our TV device by sending an infrared signal to it from the remote control.
    [Show full text]