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4th Grade – Light Unit, Spectrascopes and Refraction

Posted in 4th Grade, and Uncategorized

Students are learning about refraction, the bending of light rays, in their classroom with Ms. Childrey.  In science lab they have built a small working spectrascope.  A thin piece of plastic in the eyepiece has thousands of parallel  triangular scratches.  Each scratch acts like a prism to refract light waves entering the spectrum tube through a slit in the end opposite the eyepiece.  Students each assembled their own scope and will be bringing it home to keep.  

When looking at a light source, the scratched plastic, called a diffraction grating, breaks the light up into its constituent colors.  With a white light, we get to see the colors of the rainbow.  With some other kind of light source, say a neon light in a restaurant window, we see only the colors given off by the light, mostly reds, oranges and yellows.  Scientists use spectroscopes for many different kinds of analyses.  One way astronombers use them is to determine the elemental composition of stars.  Each element has it’s own unique spectrum.

We had an extensive discussion about safety while building our spectrascopes.  Please remind your student about the danger of looking directly at the sun.

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