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R A I N B O W S

R A I N B O W S. GROUP 6 . Rainbows Before History. People did not know how to explain rainbows Common ways to rationalize rainbows were religious beliefs and magic Leprechauns and their pot o’ gold Chakras, or energy centers. Rainbow Mythology. Greek goddess Iris, of Rainbows

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R A I N B O W S

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  1. RAINBOWS GROUP 6

  2. Rainbows Before History • People did not know how to explain rainbows • Common ways to rationalize rainbows were religious beliefs and magic • Leprechauns and their pot o’ gold • Chakras, or energy centers

  3. Rainbow Mythology • Greek goddess Iris, of Rainbows • Messenger and water-bringer of the gods • Norse bridge Bifrost • During Ragnorak, connects Earth to Asgard • Australian Aboriginal Rainbow Serpent • Creator of all things, lives in the wild

  4. The Epic of Gilgamesh • Used Rainbows as a sign of war • Buddhism & Nirvana • Second highest state of being • Noah’s Ark, the sign of peace • The “calm after the storm”

  5. The Symbol of Diversity • Often used now as a symbol of overcoming diversity • Used in the 50’s to support racial equality • Used currently as a symbol for gay rights

  6. History • Aristotle • 384-322 BCE • First to give attention to rainbows • Set the ground work for centuries to come. • Seneca the Younger • 65 CE • Noticed that rainbows always appear opposite the Sun • Foreshadowed Newton’s experiments dealing with prisms and refraction

  7. History • Sir Isaac Newton • 1642-1727 • Demonstrated that white light is a composition of all the colors in the rainbow • Discovered that red light is refracted less than blue light • Rene Descartes • 1637 • The first to discuss the formation of rainbows • Studied single water droplets and how it interacts with light • Famous book: L’arc en Ciel

  8. Spectrum of a Rainbow • Red: greatest wavelength • Sunlight is the combination of all colors of light. • Different wavelengths cause different angles of refraction

  9. Mathematics of a rainbow • Product of light leaving raindrops • Differing angles of refraction • Snell’s Law: • Total Deflection • D = (I – r) + (180-2r) + (1 - r) • We use caustic rays • Take derivative of D with respect to I • Use Snell’s Law

  10. WHY THE BOW?

  11. ANTISOLAR POINT • The point where an imaginary ray connecting the sun and yourself meets the sky. • The rainbow is also 40 – 42 degree around the antisolar point. *Shadow of our head marks the point 180° away from the sun*

  12. ANTISOLAR POINT co.. • Why is this Important? • The antisolar point tells us where we can expect a rainbow to form • The higher the sun the lower the rainbow; the lower the sun the higher the rainbow • Another person may not see they same rainbow.. • they may see the light reflecting off other raindrops from a completely different angle

  13. WHAT BOW? • The bow shape is actually part of a circle of light that is cut off by the horizon that obstruct it called a “glory”. • At a high altitude such as in an airplane.(horizon do not block the observer point of view)

  14. “Oh My God It’s A Double Rainbow” • A double (secondary) rainbow occurs when the light enters the raindrop and reflects not once, but twice • The angle of reflection is slightly larger than normal, approximately 50 degrees • Secondary rainbows are not nearly as vivid as primary rainbows making them much harder to see

  15. More than Two Rainbows • Double rainbows are impressive, but it is theoretically possible for there to be up as many as four visible rainbows • This is possible when there is standing water in the area • The primary and secondary rainbows are BOTH reflected off this standing water, creating an additional 2 rainbows that usually come in at a slightly steeper angle • Most of the time, the highest number of visible rainbows is constricted to three

  16. Tertiary and quaternary rainbows • In addition to the primary and secondary rainbows seen in a direction opposite to the sun, it is also possible (but very rare) to see two faint rainbows in the direction of the sun. These are the tertiary and quaternary rainbows, formed by light that has reflected three and four times within the rain drops, respectively.

  17. Supernumerary Rainbow • A supernumerary rainbow is an infrequent phenomenon, consisting of several faint rainbows on the inner side of the primary rainbow, and very rarely also outside the secondary rainbow. Supernumerary rainbows are slightly detached and have pastel color bands that do not fit the usual pattern. • It is not possible to explain their existence using classical geometric optics. The alternating faint rainbows are caused by interference between rays of light following slightly different paths with slightly varying lengths within the raindrops.

  18. Monochrome rainbow • Occasionally a shower may happen at sunrise or sunset, where the shorter wavelengths like blue and green have been scattered and essentially removed from the spectrum. Further scattering may occur due to the rain, and the result can be the rare and dramatic monochrome rainbow.

  19. Moonbows • “Moonbows” are rainbows produced by light reflected off the surface of the moon rather than from direct sunlight. They are often perceived as white and may be thought of as monochrome.. Long exposure photographs will sometimes show the color in this type of rainbow.

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