Starlight

Standard I

Students will understand the scientific evidence that supports theories that explain how the universe and solar system developed.

Objective 01

Describe the big bang theory and evidence supporting it.

Indicator a

Determine the motion of a star relative to Earth based on a red or blue shift in the wavelength of light from the star.

Indicator b

Explain how evidence of red and blue shifts is used to determine whether the universe is expanding.

Intended Learning Outcomes:

  1. Use Science Process and Thinking Skills
    1. Use comparisons to help understand observations and phenomena.
    2. Evaluate, sort, and sequence data according to given criteria.
    3. Construct models, simulations and metaphors to describe and explain natural phenomena.

Description: Students will analyze light given off by glowing elements using a spectroscope. They will relate the spectrum given off by a stationary source to one that is "red-shifted".

Time Required: 40 minutes

Student Background: Students should know that elements are pure substances with distinct properties. One of the properties is the banding pattern seen through a spectroscope when substances are burned or heated. The radiation is given off in various wavelengths which can be viewed with a spectroscope or diffraction grating. If the object giving off the radiation was moving away from the viewers the lines will shifted toward the red end of the spectrum.

Note to Teacher: There are several ways to generate light for this demonstration. The most difficult for the students is to burn small amounts of the various metal salts in a flame on a wire loop, the best way for students to see spectra is to buy the vapor tubes of each element or mixture of elements and power source (a tesla coil also works) that runs electricity through them. This is more expensive but they last a long time. You can also find commercially made light bulbs with mercury vapor, argon, and neon in them. If you have tubes with "air" in them, students could figure out what gases are in air, You would also need tubes of nitrogen, oxygen, and carbon dioxide for them to look at.

Materials:

  • Salts or vapor tubes of several elements (sodium, potassium, lithium, strontium, hydrogen, helium, argon, mercury, etc.)
  • Student response sheet
  • Diffraction grating
  • Spectroscope
  • Colored pencils or crayons

Procedures:

  1. Hand out student sheet and go over purpose and procedures with students.
  2. Make sure students can see the spectrum on room lights.
  3. Turn out the lights and use the light source you have chosen to create light spectra.
  4. Have students color the spectra on their paper as they see it.
  5. Students finish with analysis and conclusions.