What optical effects does refraction cause in the atmosphere???

Refraction, Sunrise, Sunset Due to refraction: The sun will appear to rise sooner (by approximately two minutes) than it actually does The sun will appear to set a bit later (by about two minutes) than it actually does

Twilight sunlight can be seen well after the sun sets due to both scattering and refraction. Twilight - is the name given to the time after sunset (and immediately before sunrise) when the sky remains illuminated. amount of twilight varies..... –it adds about 30 minutes before sunrise and after sunset in mid latitudes –length of time increases with increasing latitude

The Green Flash caused by refraction recall that short wavelengths (blue and green) refract more than longer wavelengths (red). hence, blue and green light should appear along the top of the sun. but, blue light is scattered away by Raleigh scattering, leaving green.... -> the green flash the green light is usually too faint to see. but is sometimes apparent momentarily, for a second or so.

Inferior Mirages

Pond in desert Interior Mirage (more)

Inferior Mirages mirage - when an object appears to be displaced from its true position created as light passes through layers of air having different densities Inferior Mirages: formed when the air near the ground is very warm compared to the air just above it. –puddles of water on the highway - what are you actually seeing? –water/oasis in the desert

Superior Mirages

produced when you have cold air near the ground and warmer air above it. --> Superior Mirage

here is a real-world example - icebergs in Antarctica

Halo a ring of light encircling and extending outward from the sun or moon created as sunlight is refracted as it passes through ice crystals. indicates cirriform clouds (high, thin clouds composed of ice crystals) two types: –22° halo - refraction of light through randomly falling ice crystals. –46° halo - refraction of light through hexagonal column-type ice crystals. here is a 22° and 46° halo

Tangent Arcs a bright arc of light at the top of the 22° halo formed by refraction of light passing through horizontally- oriented pencil- shaped hexagonal ice crystals

Sun Dogs

What creates rainbows?

Different colors of light have different frequencies, which causes them to travel at different speeds when they move through matter. A prism separates white light into its component colors. For simplicity's sake, this diagram shows only red and violet, which are on opposite ends of the spectrum.

White light separates into different colours on entering the raindrop due to dispersiondispersion, causing red light to be refracted less than blue light.

The Steps Involved in the Process Copyright 1999 Rebecca McDowell. 1. Light from Sun strikes raindrop1. Light from Sun strikes raindrop 2. Some of the light is reflected 3. The rest of the light is refracted 4. Light splits into component colours 5. Reflected at rear of raindrop (TIR) 6. Refracted again as it leaves raindrop 7. Colors are further dispersed 2. Some of the light is reflected 3. The rest of the light is refracted 4. Light splits into component colours 5. Reflected at rear of raindrop (TIR) 6. Refracted again as it leaves raindrop 7. Colors are further dispersed Class Participation

What creates rainbows? Rainbows are generated through refraction and reflection of light in small rain drops. sun must be behind you rain drops must be ahead of you the angle between your line-of-sight and the sunlight will be 40°-42°

In a "primary rainbow", the arc shows red on the outer part and violet on the inner side. This rainbow is caused by light being refracted while entering a droplet of water, then reflected inside on the back of the droplet and refracted again when leaving it. Double Rainbow

Physics for double rainbow: reflected in raindrop twice

In a double rainbow, a second arc is seen outside the primary arc, and has the order of its colours reversed, red facing toward the other one, in both rainbows. This second rainbow is caused by light reflecting twice inside water droplets.

Where else can you see rainbow?

Circular rainbow seen while skydiving over Rochelle, IllinoisskydivingRochelle, Illinois

Photographer: Rick ScottRick Scott Photo taken on October 13, This photo shows the shadow of a jet aircraft surrounded by a gloryglory as the plane was preparing to land in London, England. FYI

History (FYI) René Descartes gave 1637 the explanation on the basis of ray optics (geometric optics), George B. Airy succeeded in 1838 to give a detailed (but approximate) description including diffraction and interference effects. Gustav Mie finally in 1908 presented the exact solution for the scattering of light by dielectric spheres – a solution which nowadays can be evaluated with fast computers, but which does not give an intuitive explanation for the calculated phenomena. (There is a special site devoted to Mie scattering by Philip Laven.)Philip Laven