Lesson 2A: Spectroscopes

Estimated Time: 3- 45 minute classes

Indicators(s): Core Learning Goal 1

1.2.7 The student will use relationships discovered in the lab to explain phenomena observed outside the laboratory.

1.4.8 The student will use models and computer simulations to extend his/her understanding of scientific concepts.

1.5.4 The student will create and/or interpret graphics (scale drawings, photographs, digital images, etc.).

1.5.6 The student will read a technical selection and interpret it appropriately.

Indicators(s): Core Learning Goal 2

2.1.2 The student will describe current efforts and technologies used to study the universe.

At least- optical telescopes, radiotelescopes, spectroscopes, satellites, space probes, manned missions.

Student Outcome(s):

The student will be able to describe the use of spectroscopes in the exploration of the universe by analyzing data.

Brief Description:

Students will construct a spectroscope and identify the spectrum of light sources. Using the computer, students will complete activities that show how researchers utilize spectroscopes in their study of the universe.

Background knowledge / teacher notes:

Spectroscopy is the study of the universe by examining an object’s spectrum. It is important for students to understand that computer models, using an algorithm (mathematical formula), convert numerical data into images. This technology allows scientists to describe atmospheres on other planets even though no one has been there. In order to validate the data from satellites, data is collected on Earth and compared to satellite data. This is called ground truthing.

 

Text Instructions for 3 Spectroscopes per Sheet

To make spectroscopes, copy these figures onto opaque paper or cardboard and cut them out. Dark construction paper works well or any paper if you photocopy black onto the reverse. Cut on the continuous lines, including the small slit, but don't cut on dotted lines. Cut the slit carefully with straight smooth edges, so as to let through some light, about 0.5 mm wide. You can cut it wider, and then form a narrow slit by the gap between two pieces of opaque tape. Now choose a data or music CD that you don't want as a CD, such as those you get unsolicited in the mail, and cut it into wedges using a pair of stout scissors. You can get about 16 useful wedges out of one CD to use as diffraction gratings. If the CD tends to crack as it is cut, you can prevent that by scoring it first with a knife before cutting with scissors. Attach a wedge of CD where indicated by the dotted outline, on the side of the paper that will become the inside (usually the unprinted side). Make sure the iridescent shiny side is exposed, but it's convenient to tape the narrow point to hold it on, and to cover the mirror-like bit near the tip. Crease on the dotted lines along a straightedge, and fold to make a little box with the CD piece inside on the bottom. Glue or tape edges closed (a to a, b to b, etc.) so that they don't leak light, but do not cover the slit. Rubber cement can be applied to all the flaps and to all the lettered regions the flaps will cover. After the cement dries, the spectroscope can be neatly folded into shape in alphabetical order. Unlabelled flaps need not be glued. It's convenient to tape at x less thoroughly or not at all so the back can be opened to look at or readjust the diffraction grating (CD piece). You're finished!

Written by Alan Schwabacher http://www.uwm.edu/~awschwab/specweb.htm#moreinfo.

Directions for using a spectroscope

Now point the slit at a light, and look through the hole at the CD. Try looking at an incandescent light bulb, and then at a fluorescent light bulb. Are all fluorescent lights the same? Try street lights and other light sources. Look at light reflected off of colored paper, or shining through transparent colored plastic, glass, or juice. How does white light from your computer monitor compare to white paper? Does the paper look the same under different lights? Can you tell why colors look ok under some street lights and not others, despite the similar appearance of the lights themselves? (The lights look similar to your eye, but not to the spectroscope.) What happens if you widen the spectroscope slit?

Written by Alan Schwabacher http://www.uwm.edu/~awschwab/specweb.htm#moreinfo.

 

Read "Spectra and What Scientists Can Learn From Them"

http://imagine.gsfc.nasa.gov/docs/science/how_l1/spectra.html

As a class discuss:

Lesson Description:

ENGAGE

Show the students several images of the earth and the universe taken by satellites and ask, "How do we get these pictures?" Help students understand that satellites do not take pictures with a camera and film, but instead use computer models based on mathematical algorithms

Using a prism generate a rainbow. Have the class discuss what they know about a spectrum.

Students will make a spectroscope. Go to http://www.uwm.edu/~awschwab/specweb.htm#moreinfo and follow the instructions for making a spectroscope. Make the smaller spectroscope (three on one page).

Be sure to darken the inside of the tube with either a black marker or black construction paper.

Education Elements:

VIDEO CLIP

This montage of Terra images from all five onboard instruments begins with a true color image of the globe and then zooms in to North America. The scene fades through a series of false color images.

http://visibleearth.nasa.gov/cgi-bin/viewrecord?239

EXPLORE

Using the spectroscope students will observe the spectra of several different light sources.

In their journal, students will record the color and location of the spectral lines they observe.

Using spectral tubes, students will observe and draw those spectral lines of different chemicals.

Ask students What does a spectroscope do?

The spectroscope separates light into its component colors by diffraction. The longer wavelengths (red) are deflected more than the shorter wavelengths (blue/violet).

Education Elements:

LESSON PLAN

This Imagine The Universe site takes the learner to an on line chemistry lesson on spectroscopy.

http://imagine.gsfc.nasa.gov/docs/teachers/lessons/supernova/supernova_chemistry.html

EXPLAIN

Journal Write: Describe the similarities and differences observed in the spectra. Based on this activity, predict ways scientists might use spectral analysis to learn about stars.

Go to http://amazing-space.stsci.edu/ and click on "Star Light, Star Bright" then click on "Heating Up and then Stellar Encounters."

Go through the tutorial.

Much of the study of the universe is through remote sensing. Many different satellites and telescopes have spectroscopes.

1. Open http://junior.apk.net/~matto/spectroscopy.htm, click # 6 "Kinds of Spectra". Read and answer the following questions in your journal:

  • What is the difference between an "emission spectrum" and a "dark line spectrum"?
  • Which type of spectrum is produced by stellar material?

GT Connection: Return to the "Chemistry of Star" homepage.

Click on # 7 "Star Spectrum". Answer the following in your journal.

What are Balmer Lines? How can they be used to learn about stars?

2. Return to the "Chemistry of Star" homepage. Click on # 7 "Star Spectrum". Click on "spectral classification system" in the description of graph (c). Record the seven spectral classes from the hottest to the coolest.

3. Click on "spectral sequence" in the last paragraph on the page. Journal write:

As you look at the spectral sequence chart, are you looking at an absorption or emission spectrum?

How do you know?

Describe the general pattern you notice as you go from the hottest stars to the coolest stars.

4. Return to the "Chemistry of Stars" homepage. Click on # 9, "Spectra of Gas Discharges". Scroll down and view the spectrum of the different elements.

Journal write: What problems may occur from viewing stars made of several elements?

Education Elements:

EDUCATIONAL BRIEF

This NASA Educational Brief provides background, explanation, and links to help the learner master an understanding of how spectroscopy is used to identify elements on the stars.

http://edmall.gsfc.nasa.gov/99invest.Site/science-briefs/ace/ed-spectro.html

EXTEND

Students, in pairs, will examine applications of image spectroscopy.

There are 3 tasks to complete. They should be done in order.

Task One:

Open http://www.achilles.net/~jtalbot/data/nebula/index.html.

Scroll down to the chart and read the description of each category under the chart.

Open the "data file" for the first nebula. You will see a series of number listed. This is how computers here would receive the data on Earth from the spectroscopes on a satellite.

Using another set of the blank spectra charts (such as the ones in the Explore), use your color pencils to draw the lines on the spectrum to correspond to the wavelength. The first column is the wavelength and the second column is the intensity. If the intensity level is low, make the line thin, and if the intensity level is high, draw the line thick.

Once you have completed this, click back and then click on "name" for the first nebula. This will give you the spectrum created by the same set of data as the spectrum you created. Notice that the spectrum on the computer goes from violet to red, turn your spectrum upside down to compare. Record your comparisons in your journal. Scroll down and observe the images of the nebula at different wavelengths. Describe in your journal how scientists use the images to learn about the nebula or any other body in space. Why is it important to know the wavelengths in the images?

Task Two:

Many of the spectroscopes used to study the universe are broad band spectroscopes, collecting data in many different wavelengths in the electromagnetic spectrum. To determine the class of a new star, scientists compare the spectra of the new star to the spectra of a known star. Practice determining the classes of stars by visiting:

http://cse.ssl.berkeley.edu/lessons/indiv/timothyk/skymap.html

On the star chart given to you, identify each star you click on and the class of star you determine it to be.

Task Three:

Spectroscopes are not used only to study stars outside of our solar system but they are used to study the most important star to us, the sun. Whereas many of the spectroscopes used to study the universe are broad based, the spectroscopes that study the sun are designed to collect data in very narrow wavelengths. Go to http://sohowww.nascom.nasa.gov/explore/EUVsun.html , and view the images of the sun taken by EIT instrument on the SOHO satellite. The color of the image is to help researchers to know what wavelength they are looking at. When the data is received from the satellite it is a series of numbers that are then turn into an image by a computer model.

In your journal record down the wavelength, the temperature, the element, and the solar activity that can be seen in that wavelength.

Describe the importance of looking at the sun in different wavelengths in terms of understanding solar activity. (Hint: Can you see sunspots in extreme ultraviolet?) In the "Go to" box at the bottom of the images scroll to "Education Links" Click on "Go to". From this page you can link to several different sites dealing with the sun. Scroll down to the "Daily Images" site and click on it. Look at the images of the sun taken in x-ray and visible.

Journal write- Do you see any relation between the x-ray images, the visible images and the ultraviolet images? Explain the importance of studying the sun in many different wavelengths.

GT Connection: Spectroscopy is not used only for the study of stars. This field is also used to study our Earth and other planets. Go to http://speclab.cr.usgs.gov/maps.html and scroll down to "Introduction to Imaging Spectroscopy Results" and click and read the information on spectroscopy.

Journal Write- Make a chart that shows the progression of remote sensing from black and white photographs through electronic absorption. Describe the advantages and disadvantages of each form of remote sensing mentioned in the reading. Click "Back" and scroll down to the section called "Environmental Applications". Click on "Summitville Mine". Read the first four paragraphs to understand how image spectroscopy is used by the USGS and how the images are obtained. The data from the satellite is feed into the computer model that creates the images based on an algorithm (mathematical formula). Scroll down to the first image and read the paragraph above the image. Click on the image to enlarge and scroll down to the key and look at the types of minerals located in the Image. Record down the major mineral(s) found around the Summitville mine. Click back and record the wavelength that this image is based on.

Scroll down to the second image and read the paragraph above the image. Click on the image to enlarge. Scroll down to the key and look at the types of minerals located in the image. Record down the major mineral(s) found around the Summitville mine. Click back and record the wavelength that this image is based on. Read the "Discussion and Summary".

Read the "Discussion Journal Write: Explain why images need to be made in different wavelengths. Describe the application of imaging spectroscopy to studying environmental science.

Education Elements:

MAP

This USGS site shows a practical example of spectral imaging. It provides materials maps that show how the new field of imaging spectroscopy allows specific absorption features, caused by chemical bonds in materials, to be mapped spatially.

http://speclab.cr.usgs.gov/maps.html

 

EVALUATE

Journal Write: What can scientists learn by observing the spectra of stars? Describe the impact spectroscopy has had on our knowledge of the universe.

 

Materials:

Manila folders or heavy construction paper to make spectroscope

Old CDs

Glue

Light sources ( ex. Fluorescent light, light bulb, grows lights, etc.)

Optional- spectrum tubes

Hand-outs of spectrum charts and EUVE star chart

Computer with Internet access

 

Resources:

Spectral charts

http://solar-center.Stanford.EDU/webcast/wcpdf/sun&stars5-8.pdf

Spectroscope directions

http://www.uwm.edu/~awschwab/specweb.htm#moreinfo

Spectroscope readings

http://imagine.gsfc.nasa.gov/docs/science/how_l1/spectra.html

http://imagine.gsfc.nasa.gov/docs/science/how_l2/spectra.html

Star Light, Star Bright

http://amazing-space.stsci.edu/

Chemistry of Spectroscopy

http://junior.apk.net/~matto/spectroscopy.htm

Nebula Images

http://www.achilles.net/~jtalbot/data/nebula/index.html

EUVE star chart

http://cse.ssl.berkeley.edu/lessons/indiv/timothyk/skymap.html

SOHO information

http://sohowww.nascom.nasa.gov/explore/EUVsun.html

USGS spectroscopy site

http://speclab.cr.usgs.gov/index.html

Sun:

http://sohowww.nascom.nasa.gov/

Hubble Space Telescope

http://www.stsci.edu/

Chandra

http://chandra.harvard.edu/about/axaf_mission.html

Imagine the Universe cite

http://imagine.gsfc.nasa.gov/docs/sats_n_data/sats_n_data.html