Globes, Prisms and a Rainbow Ray: teacher key

Rainbows, grade 10 edition, written for 10th grade. The rainbow was explained wrongly for centuries. Meet the scholars who built giant raindrops, the thinker who traced a ray, and the experiment that showed the colors were already in sunlight.

Read the book. Print this page for the key.

Questions and answers

1. How did Theodoric of Freiberg study the rainbow?
   • With a globe of water standing in for a raindrop (answer)
   • With a telescope
   • By tracing sunlight on a cloud
2. Why did Newton use a board with a hole in his crucial experiment?
   • To let only one color enter a second prism (answer)
   • To make the sunlight hotter
   • To hide the sun
3. What did the result of the crucial experiment show?
   • A prism makes colors out of white light
   • A prism only bends each color by a different amount (answer)
   • Red light turns blue
4. Why does reflection off the back of a drop not spread the colors?
   • Reflection does not depend on wavelength (answer)
   • The back of the drop is dark
   • Only violet reflects
5. In the passage, what does 'dispersion' mean?
   • A second rainbow
   • Light spread out by wavelength (answer)
   • A drop of rain falling

Words

• dispersion: spreading by wavelength
• aberration: optical blur
• tertiary: third-order
• spectrum: band of colors