SPH4UI 10 Rainbow Questions 1. 1.Is the inside red? 2. 2.Radius in degrees? 3. 3.Width in degrees? 4. 4.Comparison of light intensity inside outside Time or Day 6. 6.Direction 7. 7.If 2, where is the second bow? 8. 8.If 2, Is the inside red? 9. 9.If 2, Radius of Second? Are rainbows polarized?

SPH4UI  Blue light more readily “scattered” by air molecules  called Rayleigh Scattering; strong function of wavelength  blue light in sky has been diverted from some other path  with some blue light missing, sun looks yellow/orange/red 2

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WHY IS THE SKY BLUE ? INCOMING SOLAR RADIATION NITROGEN MOLECULE

SPH4UI WHY IS THE SKY BLUE ? SCATTERING OF BLUE LIGHT

SPH4UI Blue Haze & Selective Scatter Plants exude terpenes that react with ozone and can also selectively scatter blue wavelengths, creating a blue haze. Mountains allow for enough viewing distance to create this needed scatter. Mountains allow for enough viewing distance to create this needed scatter.

SPH4UI Atmospheric Dust & Rays Dust and salts are large enough to cause geometric scattering, and change blue skies into hazy white skies. Concentrated dust or salts beneath clouds can create white crepuscular rays of sunlight. Concentrated dust or salts beneath clouds can create white crepuscular rays of sunlight.

SPH4UI Is the night sky blue too? You bet! Just too dim to perceive – time exposure at night under moonlight shows this 8 You can find blue from scattering in other circumstances as well: water, glaciers, astrophysical reflection nebulae…

SPH4UI Red at Sunrise and Sunset Low on the horizon, the sun's light passes through nearly 12 times more atmospheric gas and aerosol, which has scattered out most short (blue) wavelengths. Longer oranges and reds then comprise the sunlight, which reflects from clouds and water.

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SPH4UI 11 The Rainbow

SPH4UI 12 Water Droplet

SPH4UI 13 Rainbow Colours 51 54

SPH4UI 14 The Angle’s

SPH4UI 15 The Angle 42 rainbow If sun is higher than 42 degrees, then alas no rainbow (it is below the horizon).

SPH4UI 16 Rainbows come in pairs… Secondary rainbow has two reflections. Red now appears lower than blue in the sky. Beautiful double rainbow in Zion National Park. The primary is brighter, and the color sequence is reversed from that seen in fainter secondary. Area between rainbows often seen to be darker than elsewhere. Note: rainbow can exist in foreground.

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SPH4UI 18 Primary

SPH4UI 19 Secondary

SPH4UI 20 Then we have Two

SPH4UI 21 Questions Which general direction will a rainbow be found in the evening?Which general direction will a rainbow be found in the evening? Why don’t you see rainbows during the middle of the day?Why don’t you see rainbows during the middle of the day? Look East 45 degrees up from your toes is still at the ground.

SPH4UI 22 The halo, and sun-dogs 22° halo around sun due to hexagonal ice crystals –often more noticeable around moon at night (less glare) Sun-dogs (parhelia) join halo, level with sun –from horizontally situated ice crystals akin to leaves falling in stable horizontal orientation –colored due to refractive dispersion through ice crystal

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SPH4UI 24 Are Rainbows Polarized? Any light that is reflected is polarized in the plane. Therefore rainbows are somewhat polarized, about 96%.

SPH4UI Sun-dog geometry 25

SPH4UI 26 Glorys and Heiligenschein (shadow-hiding) A circular rainbow about the anti-solar direction is called a glory –Sometimes 2–3 colored rings –often see shadow in middle –water droplet phenomenon The anti-solar point may also get bright due to shadow-hiding –called heiligenschein –often see from airplane over textured terrain –no, the person in the photo is not an angel

SPH4UI 27 Cool Rainbow Effects The pot of Gold? Primary and Reflected Rainbow Primary, Secondary, and Reflected Rainbow Supernumerary Reflected

SPH4UI 28 Rainbow at Night