Chapter 15 Atmospheric Optics Fig 15 CO p 414 White Clouds and Scattered Light reflection scattering Thunderstorms appear dark because the clouds cumulonimbus are about 10 km deep scattering most of the light Cloud droplets scatter all wavelengths of visible white light about equally The different colors represent different wavelengths of visible light Fig 15 1 p 417 Since tiny cloud droplets scatter visible light in all directions light from many billions of droplets turns a cloud white Fig 15 2 p 417 The sky appears blue because billions of air molecules selectively scatter the shorter wavelengths of visible light more effectively than the longer ones This causes us to see blue light coming from all directions Fig 15 4 p 418 crepuscular rays The scattering of sunlight by dust and haze produces these white bands of crepuscular rays Fig 15 7 p 419 Because of the selective scattering of radiant energy by a thick section of atmosphere the sun at sunrise and sunset appears either yellow orange or red The more particles in the atmosphere the more scattering of sunlight and the redder the sun appears Fig 15 8 p 420 The behavior of light as it enters and leaves a more dense substance such as water Fig 15 11 p 421 Fig 15 12 p 422 The Mirage Inferior mirage The road in the photo appears wet because blue skylight is bending up into the camera as the light passes through air of different densities Fig 15 15 p 424 Inferior mirage The road in the photo appears wet because blue skylight is bending up into the camera as the light passes through air of different densities Fig 15 16 p 424 superior mirage The formation of a superior mirage When cold air lies close to the surface with warm air aloft light from distant mountains is refracted toward the normal as it enters the cold air This causes an observer on the ground to see mountains higher and closer than they really are Fig 15 17 p 425 A 22 halo around the sun produced by the refraction of sunlight through ice crystals Fig 15 18 p 425 The formation of a 22 and a 46 halo with column type ice crystals Fig 15 19 p 426 Halo with an upper tangent arc Fig 15 20 p 427 Refraction and dispersion of light through a glass prism Fig 15 21 p 427 Platelike ice crystals falling with their flat surfaces parallel to the earth produce sundogs Fig 15 22 p 427 The bright areas on each side of the sun are sundogs Fig 15 23 p 428 A brilliant red sun pillar extending upward above the sun produced by the reflection of sunlight off ice crystals Fig 15 24 p 428 Optical phenomena that form when cirriform ice crystal clouds are present Fig 15 25 p 429 When you observe a rainbow the sun is always to your back Fig 15 26 p 429 Rainbows Sunlight internally reflected and dispersed by a raindrop a The light ray is internally reflected only when it strikes the backside of the drop at an angle greater than the critical angle for water b Refraction of the light as it enters the drop causes the point of reflection on the back of the drop to be different for each color Hence the colors are separated from each other when the light emerges from the raindrop Fig 15 27 p 430 The formation of a primary rainbow The observer sees red light from the upper drop and violet light from the lower drop Fig 15 28 p 430