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RAY OPTICS

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1. Mechanisms Particle/Molecule-light interactions responsible for creating optical effects. These interactions include: reflection, scattering, refraction and diffraction. 2. Air, Dust, Haze Optical effects resulting from the interaction of light with air, dust and haze particles. These effects include: crepuscular rays, blue skies, blue haze and sunsets.

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3. Ice Crystals Optical effects resulting from the interaction of light with ice crystals. These effects include: sundogs, sun pillars and halos. 4. Water Droplets Optical effects resulting from the interaction of light with water droplets. These effects include: cloud iridescence, rainbows and a silver lining along the edge of clouds Mirages: Fata Morgana

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1. Ray Optics The Law of Reflection Examples: sun glint - reflection of the solar disk off water. sparkling of snow surface - snow crystals acting like little mirrors. Example photo. sun pillars - caused by reflection of sunlight off crystals.

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Refraction The law of refraction is n1sinq1= n2sinq2 Examples of refraction Refraction causes a setting sun to look flat Twinkling, or scintillation, if stars Twilight caused by refraction and scattering. Atmospheric mirages are caused by light passing through and being refracted by air layers of different densities. Densities differences can be caused by temperature changes. Fata Morgana Halos - appear with ice clouds. Crystals have to be small 15 or 20 microns. Shadows on the bottom of a pool.

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Scattering of Light

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2. Air, Dust, Haze Sunrays - Crepuscular rays

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Lunar rays Anti-crepuscular rays Cloud Shadows Earth's Shadow Mountain Shadow

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2. WHY IS THE SKY BLUE? The blue color of the sky is due to Rayleigh scattering. As light moves through the atmosphere, most of the longer wavelengths pass straight through. Little of the red, orange and yellow light is affected by the air.

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PROJECTS TO DO TOGETHER PROJECT 1 - Split light into a spectrum What you need: a small mirror, a piece of white paper or cardboard, water a large shallow bowl, pan, or plastic shoebox a window with direct sunlight coming in, or a sunny day outdoor What to do: Fill the bowl or pan about 2/3 full of water. Place it on a table or the floor, directly in the sunlight. (Note: the direct sunlight is important for this experiment to work right.) Hold the mirror under water, facing towards the sun. Hold the paper above and in front of the mirror. Adjust the positions of the paper and mirror until the reflected light shines on the paper. Observe the colored spectrum. What happened ?

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3. Ice Crystals Sundogs (mock suns or parhelia) Sundogs, also known as mock suns or "parhelia", are a pair of brightly colored spots, one on either side of the sun.

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Sun Pillars vertical shafts of light A sun pillar is a vertical shaft of light extending upward or downward from the sun

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Halo

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Coronas produced by diffraction of light. This 'crown' of light around the sun or moon is called the corona.

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4. Water Droplets Iridescent Clouds

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What is a rainbow? Where is the sun when you see a rainbow? What makes the bow?

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What makes the colors in the rainbow? What does a rainbow look like through dark glasses?

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What are Reflection Rainbows? What makes a double rainbow? Simulating a Rainbow

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Silver Lining and Cloud Iridescence produced through diffraction of sunlight

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Mirage Roadmirage

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Trees shown which are normally invisible below horizon, a superior mirage refracted from above Sunrise first light caused by super-refracted sunlight Double sun sunrise caused by a super-refracted sun