TBoard by muted labs
Light Inside a Raindrop — lesson illustration Foundation

WEATHER & EARTH

Light Inside a Raindrop

  • 9 spell
  • 5 known
  • 4 open
  • 3 math
Print / Download PDF
Play app demo
Lesson preview

AFTER THE RAIN

The RAIN stops. The CLOUDS break in the west, and low afternoon sun spills across a wet yard. Turn your back to that light, look toward the fading shower, and a curved band of color hangs in the air, red along the outside and violet along the inside. Nothing is up there but falling water. Each drop works like a PRISM, a clear object that bends light and spreads it into a SPECTRUM, the full set of colors hidden inside plain white sunlight.

  1. SPELL
    CLOUDS
  2. SPELL
    RAIN
  3. KNOWN
    What is the name for a clear object that bends light and spreads it into colors?
    Answer: PRISM
  4. KNOWN
    What is the name for the full set of colors hidden inside plain white sunlight?
    Answer: SPECTRUM
  5. OPEN
    When you notice a band of color in the sky, which color do you look for first?
  6. MATH
    A rainbow is usually named with 7 colors. Red sits at the outside edge and violet at the inside edge. How many colors lie between those two edges?
    Answer: 5

INSIDE A RAINDROP

Sunlight looks white, but it is really a mixture of colors traveling together. When a beam enters a raindrop, it slows down and bends. That bending is called REFRACTION. The beam crosses the drop, strikes the curved back WALL, and bounces off in a REFLECTION. Then it bends again on the way out. Red light bends the least and violet bends the most, so the colors leave the drop at slightly different ANGLES. That is why one drop can send your eye a single pure color.

  1. SPELL
    WALL
  2. SPELL
    ANGLES
  3. KNOWN
    When a beam of light enters a raindrop, it slows down and bends. What is that bending called?
    Answer: REFRACTION
  4. KNOWN
    Inside the drop, the light hits the curved back wall and bounces off. What is that bouncing called?
    Answer: REFLECTION
  5. OPEN
    If a single raindrop could send you just one pure color, which color would you want it to send?
  6. MATH
    Red light leaves a raindrop at about 42 degrees, and violet light leaves at about 40 degrees. How many degrees apart are they?
    Answer: 2

DROPS, NOT RAIN

Rain is not really what a rainbow needs. Drops are. Spray from a waterfall, a garden HOSE, or ocean surf can lift the same COLORS into the air on a sunny day. In fog the droplets are so tiny that the colors smear together and the arc turns pale and washed out. That ghostly white band is a fogbow. On a clear night with a bright full MOON, faint light passing through falling rain can build a moonbow, so dim that most eyes read it as gray.

  1. SPELL
    HOSE
  2. SPELL
    MOON
  3. SPELL
    COLORS
  4. OPEN
    A moonbow is so faint that most eyes read it as gray. What do you imagine it would feel like to spot one?

YOUR OWN RAINBOW

So you cannot walk up to a rainbow or stand underneath it. It is a direction, not a place. The arc is always centered on the antisolar POINT, the SPOT directly opposite the sun, straight out past the shadow of your own head. The colored band sits about 42 degrees away from that CENTER. Step sideways and the arc slides with you, rebuilt from new drops. Your friend beside you catches light from different drops, so you never share the same rainbow.

  1. SPELL
    SPOT
  2. SPELL
    CENTER
  3. KNOWN
    The place directly opposite the sun, straight out past the shadow of your own head, is the antisolar what?
    Answer: POINT
  4. OPEN
    Your friend beside you is seeing a rainbow built from different drops than yours. How would you describe yours to them?
  5. MATH
    A rainbow's colored band sits about 42 degrees out from its center in every direction. How many degrees is that all the way across, from one edge, through the center, to the other edge?
    Answer: 84

Enjoy the lesson? Get the TBoard app

Download on the App StoreGet it on Google Play
Sources consulted for the facts in this lesson