Fig. 15-CO, p. 414

Chapter 15:

Atmospheric Optics

White Clouds and Scattered Light

• reflection

• scattering• Thunderstorms appear dark because the cloudsThunderstorms appear dark because the clouds

(cumulonimbus) are about 10 km deep, scattering(cumulonimbus) are about 10 km deep, scatteringmost of the light.most of the light.

Fig. 15-1, p. 417

Cloud droplets scatter all wavelengths of visible white light about equally. The different colors represent different wavelengths of visible light.

Fig. 15-2, p. 417

Since tiny cloud droplets scatter visible light in all directions, light from many billions of droplets turns a cloud white.

Fig. 15-4, p. 418

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. 15-7, p. 419

crepuscular rays

The scattering of sunlight by dust and haze produces these white bands of crepuscular rays.

Fig. 15-8, p. 420

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. 15-11, p. 421

The behavior of light as it enters and leaves a more-dense substance, such as water.

Fig. 15-12, p. 422

Fig. 15-15, p. 424

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.

The MirageThe Mirage

Inferior mirage

Fig. 15-16, p. 424

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.

Inferior mirage

Fig. 15-17, p. 425

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.

superior mirage

Fig. 15-18, p. 425

A 22° halo around the sun, produced by the refraction of sunlight through ice crystals.

Fig. 15-19, p. 426

The formation of a 22° and a 46° halo with column-type ice crystals.

Fig. 15-20, p. 427

Halo with an upper tangent arc

Fig. 15-21, p. 427

Refraction and dispersion of light through a glass prism.

Fig. 15-22, p. 427

Platelike ice crystals falling with their flat surfaces parallel to the earth produce sundogs.

Fig. 15-23, p. 428

The bright areas on each side of the sun are sundogs.

Fig. 15-24, p. 428

A brilliant red sun pillar extending upward above the sun, produced by the reflection of sunlight off ice crystals.

Fig. 15-25, p. 429

Optical phenomena that form when cirriform ice crystal clouds

are present.

Fig. 15-26, p. 429

When you observe a rainbow, the sun is always to your back.

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.

Rainbows

Fig. 15-27, p. 430

Fig. 15-28, p. 430

The formation of a primary rainbow. The observer sees red light from the upper drop and violet light from the lower drop.