Chapter 12 — THE GOVERNING FUNDAMENTALS OF METEOROLOGY 



CENTRIFUGAL 



FORCE 



(OUTWARD) 



CENTRIPEDAL 



FORCE 



(INWARD) 



209.10 

 Figure 12-11. — Simplified illustration of centri- 

 petal and centrifugal force. 



LOW 

 VELOCITY 



HIGH VELOCITY 



LOW 

 VELOCITY 



209.11 

 Figure 12-12. — Example of Bernoulli's theorem. 



and even the light reflected by the objects which 

 it strikes, affect the eye and produce the 

 sensation of vision. Too, much of the world's 

 work and much of our recreation are made 

 possible by the use of light. 



Light, too, when acting in conjunction with 

 some of the elements of the atmosphere 

 produces such atmospheric phenomena as halos, 

 coronas, mirages, and rainbows. 



In this section of the chapter we will discuss 

 some of the theories of light, even though 

 scientists do not yet have a complete explanation 

 of the nature of light, its properties, what 

 happens to these light rays 

 their source, and some of 

 phenomena produced by light. 



after they leave 

 the atmospheric 



LIGHT 



Light is the portion of the electromagnetic 

 spectrum that can be detected by the human 

 eye. It travels at the same speed as all other 

 electromagnetic radiation (186,000 miles per 

 second). However, the characteristics of light 

 are considerably different from other regions 

 of the electromagnetic spectrum because of the 

 differences in wavelength and, consequently, in 

 frequency. 



Sources of Light 



of a certain kind. For the purpose of illustra- 

 tion, the Santa Ana wind is used. The condition 

 which produces this wind is a high-pressure 

 area with a strong pressure gradient situated 

 near Salt Lake City, Utah. This gradient directs 

 the windflow into a valley leading to the town 

 of Santa Ana near the coast of California. As 

 the wind enters the valley, its flow is sharply 

 restricted by the funneling effect of the mountain 

 sides. This restriction causes the wind speed 

 to increase, bringing about a drop in pressure 

 in and near the valley. This pressure drop in 

 and near a valley, caused by the Bernoulli 

 effect, is a valuable forecasting aid in pre- 

 dicting this type of wind. 



OPTICAL PHENOMENA 



Light sent out by such bodies as the sun or 

 the stars or from artificial sources such as lamps 



There are considered to be two sources of 

 light — the natural light, nearly all of which we 

 receive from the sun, and artificial light, such 

 as light from electric lamps, the light of a 

 fire, or the light from fluorescent tubes 

 produced by the action of ultraviolet light on 

 chemicals enclosed in the tube. 



Luminous bodies are those bodies which 

 produce their own light. We think of the sun 

 and the stars as luminous bodies. Illuminated 

 or nonluminous bodies are those bodies which 

 merely reflect the light they receive and are 

 therefore visible because of this reflection. 



Theory 



When light is emitted from a source, waves 

 of radiation travel in straight lines and in all 

 directions. A simple example of motion similar 



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