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Dispersion

Dispersion. P. 453. Dispersion. The 7 different wavelengths (ROYGBIV) of white light all travel at the same speed in a vacuum . When light encounters matter, however, the colours of light to slow down to different speeds . Therefore, refraction will also be different for each colour .

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Dispersion

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  1. Dispersion P. 453

  2. Dispersion • The 7 different wavelengths (ROYGBIV) of white light all travel at the same speed in a vacuum. • When light encounters matter, however, the colours of light to slow down to different speeds. • Therefore, refraction will also be different for each colour. • Shorter wavelengths are more affected by atoms in a material and refract (bend) more than longer wavelengths. Red bends least, violet the most.

  3. This is why the order ROYGBIV is always the same when white light is refracted

  4. Optical Phenomena in Nature P. 469-473

  5. The Illusion of Apparent Depth • Objects in the water viewed from above the water are deeper and farther than they appear. Birds which dive out of the air to catch fish must take this illusion into account!

  6. When you look at an angle into the water, it is deeper than it looks!

  7. If he sees a fish, where should he aim his spear?

  8. If the fish aimed its stream of water where the insect appears to be…..it would stay hungry.

  9. Shimmering – apparent movement Hot air is less dense than cool air and they refract light differently but the change from hot to cool is gradual  shimmering + the air is constantly moving!

  10. Mirages • A larger scale than shimmering • Usually occurs above a hot roadway or desert • The hot air above the ground causes the light to refract upward. • We “see” the effect because we assume the light has travelled in a straight line.

  11. You may even see what appears to be reflections as part of the mirage!

  12. If you see something like these, however….it is either really there or you are hallucinating!

  13. Rainbows • Sun must be behind you • The light refracts and disperses as it enters water droplets • The light internally reflects inside the raindrop • As the light exits the droplets, a second refraction occurs – and more dispersion into the colours of the spectrum

  14. All 7 colours (ROYGBIV) leave each raindrop, however the colours we see come from different droplets at different heights in the sky.This is why red is at the top of a rainbow and violet is at the bottom

  15. Double Rainbows – droplets higher up have the light internally reflect twice inside. 1 Spherical droplet2 Places where internal reflection of the light occurs3 Primary rainbow4 Places where refraction of the light occurs5 Secondary rainbow6 Incoming beams of white light7 Path of light contributing to primary rainbow8 Path of light contributing to secondary rainbow9 Observer10 Region forming the primary rainbow11 Region forming the secondary rainbow12 Zone in the atmosphere holding countless tiny spherical droplets

  16. Sundogs • Usually occur at sunrise or sunset on cold clear days and there are ice crystals in the air. • The ice crystals refract the sun’s rays.

  17. Ice crystals in the air refract and sometimes disperse the light

  18. HOMEWORK: Page 467 # 1,2,3,7,8 • Another worksheet – math problems / ray diagrams • Tomorrow– shortrefraction quiz • Tomorrow– begin lenses • Next Tuesday – article summary #2 due

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