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11.3 – Optical Phenomena in Nature

11.3 – Optical Phenomena in Nature. Rainbows. The sun must be behind you to see a rainbow, and it must reflect off of water droplets in the air The colours you see are due to a combination of reflection, refraction, and dispersion through these water droplets. Rainbows.

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11.3 – Optical Phenomena in Nature

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  1. 11.3 – Optical Phenomena in Nature

  2. Rainbows • The sun must be behind you to see a rainbow, and it must reflect off of water droplets in the air • The colours you see are due to a combination of reflection, refraction, and dispersion through these water droplets

  3. Rainbows • A rainbow forms when light enters a water droplet and refracts, reflects off the inner surface of the droplet, and then refracts again when leaving the droplet, causing dispersion

  4. Sundogs • Sundogs appear as bright spots on both sides of the sun • They appear when ice crystals in the atmosphere refract sunlight (as opposed to water droplets for rainbows)

  5. The Illusion of Apparent Depth • An image can be formed by either reflection of light (as in a mirror) or refraction of light • You can use ray diagrams to show where the refracted image is located • Apparent depth is an optical effect in which the image of an object appears closer than the object itself • Often occurs when you are looking from the air into water

  6. The Illusion of Apparent Depth • Light rays from the object travel to your eyes, but the rays have refracted at the surface of the water • The image of the box is located by tracing the refracted rays backwards until they meet (just like for reflection!) • Notice that the box on the bottom of the pool looks like it is higher than it actually is – in reality, the bottom of the pool is deeper than it appears to be

  7. Shimmering and Mirages • Shimmering and mirages are caused by refraction of light in unevenly heated air • When light travels through air at different temperatures, it refracts because hot air is less dense than cold air • Because there is no distinct boundary between sections of air at different temperatures, the light does not bend at one specific point – it travels along a curved path • Also, since air is usually moving, the direction and the amount of bending are constantly changing

  8. Shimmering • You can see this in the air above any hot surface – the objects look wavy

  9. Mirages • Occurs on a much larger scale than shimmering • Most commonly seen in very hot deserts or on highways – the sand or paved surface becomes extremely hot after being in sunlight for several hours • The hot ground heats the air just above it, making the lower layer of air much hotter than the higher air • When sunlight reaches the hot air near the ground, the sunlight is refracted upwards

  10. Mirages • An object that appears to be on the ground but is not really there is called a mirage • The solid, curved line below shows the path of light from the sky; the dashed line shows how your brain interprets the scene

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