Make rainbows!

Posted 21 January 2010
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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 shows the primary rainbow and its light rays.

Secondary shows 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 parallel light rays from the sun refracting and reflecting from raindrops at the top and bottom of the rain curtain. Outgoing beams show where the rainbow is visible.

• Multi-drop mode shows three light rays refracting from three raindrops at different altitudes. The color you see depends on the angle of refraction.

• Single-drop mode shows the path inside one 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.

DRAG YOUR OBJECTS:
• Drag the sun-like object (top and right side) to change the angle of the light rays. This changes the time of day.
• Drag the humanoid object to see how distance from the rain affects rainbow
location in the sky.
• In multi-drop mode, drag raindrops up and down to see how altitude affects viewing on the ground.

Applet and illustrations copyright (C) 2003 Tom Whittaker, S.V. Medaris, and Steve Ackerman. The Motion-W® and Bucky Badger® logos are trademarks of the University of Wisconsin-Madison.

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