Make a rainbow

Rainbows are one of the wonders of the natural world: But why do you sometimes see one rainbow, and other times a double? Why do you always see rainbows with your back to the sun? How do they really work? Operate your own rainbow, then find out! OPERATING INSTRUCTIONS: CHOOSE YOUR ‘BOW:

• Primary checkbox enables the primary bow and its light rays.
• Secondary checkbox enables the secondary bow and its light rays. Notice this bow is seen from different places on the ground; some observers can see a primary, but not a secondary, or vice versa. Lucky people can see both rainbows.
• To see both ‘bows (but no light rays), uncheck both rainbow boxes in Rain Curtain Mode.

PICK YOUR MODE:

• Rain Curtain mode shows two parallel light rays (beams) from the sun refracting off a raindrop at the both the top and bottom of the rain curtain. Outgoing beams show where the rainbow is visible.
• Multi-drop mode mode shows three parallel light rays refracting off three raindrops at different altitudes. The color you see depends on the angle of refraction.
• Single-drop mode mode shows the path inside a single drop. Change from primary to secondary to see how the light takes a different path for each rainbow. A secondary rainbow is reflected twice, so it’s dimmer.

Note that primary or secondary bows may be used with each mode.

DRAG YOUR OBJECTS:

• Drag the sun around (across the top and up/down the right side) to change the angle of the parallel light rays from the sun and simulate a time-of-day.
• Drag the person back and forth to see the effect of observer distance from the rain.
• When in “multi-drop mode” drag the refracting drops up and down.