GROUP SIZE: Large
TIME: 2-45 minute periods
TYPE OF ACTIVITY: Student Investigation ,
TEACHING STRATEGY: Guided Discovery Expository
CONCEPTS: Spectrum Spectography Elements
SKILLS: Experimentation Recording and Interpreting Data
Objectives: To demonstrate that various elements can be distinguished by their light spectrum; to relate the experiment to the OAO satellite.
Materials: Mailing tube; aluminum foil; alcohol burner; diffraction grating or prism; scissors; pliers; straightened paper clips; elements such as: table salt – sodium chloride, boric acid – baron, copper sulfate = copper, limewater – calcium, lithium, barium and strontium.
Teacher Background Information:
The Orbiting Astronomical Observatory OAO is an unmanned satellite designed to give astronomers their first sustained look into the universe from above the obscuring and distorting effects of the Earth’s atmosphere. The OAO is the largest of the NASA scientific satellites under development and weighs nearly four thousand pounds” It is also the most electronically complex unmanned spacecraft ever developed by the U.S. It contains more than 440,000 separate parts and 30 miles of electrical wiring.
One thousand pounds of the weight is electronic astronomical observing instruments. It is a 10-foot long, eight-sided cylinder, seven feet wide. with the solar panels extended, the overall width of the spacecraft is 21 feet.
Future OAO spacecraft will have such a precise control system for pointing the scientific instruments that it could look at the width of a pencil 10 miles away. This precision is possible because of the six telescope star trackers mounted on the main body of the spacecraft.
The telescopes aboard the spacecraft will be used for several things. They will help map certain parts of the sky now hidden by direct clouds; clearer views of the planets will also be possible. They will make studies of stars to determine their chemical composition and learn more about the birth of stars. There will also be experiments which are concerned with the study of x-ray and gamma ray spectral regions. Finally, the telescopes will study stars and nebulae in the ultraviolet spectrum not visible from the Earth.
The following activity should help students to understand more about using the simple glass prism to show the spectrum and demonstrate how elements can be distinguished by their specific light spectrum.
- Ask the students to name the seven colors which make up the visible spectrum. “Roy G. Biv” is one way of helping students remember the colors: red, orange, yellow, green, blue, indigo and violet. Use a prism or diffraction grating or discuss a rainbow to demonstrate what white light is made up of. Talk about ultraviolet light being near the blue band of the visible light portion of the spectrum. Discuss the damage ultraviolet light can do. Why do we use sunglasses on very bright days? Why do we burn if we stay in the sun without protection for too long?
- If you have fluorescent minerals or fluorescent chalk, have the students observe the effect of ultraviolet light when you shine a light on them. Ask the students why, if the sun gives off so much ultraviolet light, we don’t burn up. Tell them that the OA0 will study ultraviolet light that cannot penetrate our atmosphere by looking at it above the atmosphere and this information could lead to revisions of present theories of stellar origin and evolution;
- To help students understand the spectrum and how various elements can be distinguished by their light spectrum, have the students
a. take the prism or diffraction grating and place it in one end of the mailing tube;
b. attach aluminum foil on the other end with elastic
c. cut a slit in the aluminum foil;
d. light the alcohol lamp;
e. place a clean paper clip in the pliers, dip into element to be tested and place over flame;
f. hold prism end up to the eye and observe color spectrum of specific element;
g. discuss the visible spectrum that is observed and record in notebook the name and the colors observed;
h. change the paper clip for each element tested and repeat the test for all the elements you have.