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Optical Phenomena

Optical Phenomena. How light can trick us. Naturally Occurring Phenomena. Apparent depth Flattened sun and sunsets Mirages Shimmering Rainbows. Apparent depth. The depth that an object appears to be due to the refraction of light in a transparent medium Eg . Looking into water from above

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Optical Phenomena

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  1. Optical Phenomena How light can trick us

  2. Naturally Occurring Phenomena • Apparent depth • Flattened sun and sunsets • Mirages • Shimmering • Rainbows

  3. Apparent depth • The depth that an object appears to be due to the refraction of light in a transparent medium • Eg. Looking into water from above • Light will refract away from the normal travelling from water into air because air is faster • Our brains don’t acknowledge that the light is refracted, so we extend the refracted ray straight back, creating a virtual source of the light rays

  4. Apparent Depth objects in water appear closer to the surface pencil in water appears bent

  5. “Flattened” Sun • When the sun nears the horizon, it appears to be flattened during a sunset • Light from the bottom of the sun is refracted more than light from the top • This is because the air lower in the atmosphere is more dense, slowing the light more • Rays from the bottom of the Sun have a greater angle of incidence

  6. Flattened Sun

  7. Mirages • A virtual image that forms as a result of refraction and total internal reflection in Earth’s atmosphere • This is the result of light travelling through different air temperatures • The index of refraction decreases as air gets warmer, causing the light to bend farther away from the normal • Total internal reflection occurs in the hottest layer, usually on the Earth’s surface • The ray travels back through to the cooler air and bends back toward the normal

  8. Mirages • When the light reaches our eyes, we think it travelled in a straight line • This results in an image of the sky appearing to be on the pavement or sand

  9. Mirages

  10. Shimmering • Also caused by light refracting through different air temperatures • Air closer to the lake is warmer, so the light refracts in the same pattern as it does near hot pavement • Total internal refraction occurs in the lowest, warmest layer causing multiple virtual images on the water’s surface

  11. Shimmering

  12. Rainbows • Rainbows are a result of the dispersion of white light into its 7 colour components • Remember: red light is refracted less than violet due to its speed ROYGBIV • Rainbows are produced by water droplets 3 steps: Dispersion of white light by the rain drop Partial internal reflection at the back of the rain drop Refraction of the light exiting the rain drop

  13. Rainbows • Our eyes see the final refraction, and projects these rays backwards to form a virtual image of a rainbow • You can only see a rainbow when the sun is behind you

  14. Rainbow

  15. Picture Credits Apparent Depth http://wpcontent.answers.com/wikipedia/commons/6/62/Pencil_in_a_bowl_of_water.png Water Mirages http://img2.blogabond.com/UserPhotos/1937/580/WaterMirage.jpg http://www.kookynet.net/media/k3832_p-mirage-simpson.jpg Mirage Diagram http://image.tutorvista.com/content/light-refraction/mirage.jpeg

  16. Picture Credits Moon shimmering http://www.boatnerd.com/news/newsthumbs/images/Moon-10-25-04-dcr.jpg http://jamminwithjay.com/images/080612_alaska/Alaska_074.JPG Rainbow http://www.alaska-in-pictures.com/data/media/13/rainbow-over-the-muldrow-glacier_1127.jpg http://www.rebeccapaton.net/rainbows/formatn.htm

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