ความคิดเห็นที่ 14
ถ้าเอาสมการ คิดคำนวน
http://apollo.lsc.vsc.edu/classes/met130/notes/chapter19/hw/ch19_homework.html
แสลผ่านอากาศเกิดการกระเจิงscattering แสะผ่านอากาศร้อนเย็นเกิดการหักเห
จากรูปสมการข้างล่างเกิดinferior mirageแสงโค้งขึ้นคือ Rc > 0.
1. Air molecules have sizes of D = 0.0001 to 0.001 micrometers, which are much smaller than the wavelengths of visible light (l = 0.4 - 0.7 micrometers). The air molecules, therefore, cause Rayleigh scattering. The ratio of scattered intensity of radiation Iscat to the incident radiation intensity Io is given by:
where a = 1.59x10-23 kg, r is the air density, nair is the refractive index, and x is the path length traveled through the air by the light. The refractive index of a particular wavelength of radiation is defined as Co/Cair where Co is the speed of the light in a vacuum (3x108 m/s) and Cair is the speed of the light in air.
Make a plot of Iscat/Io for violet light (l=0.4 micrometers) versus distance. Beyond approximately what distance will you likely not see a violet object? Assume that r = 1 kg m-3 and n = 1.0002817.
2. As discussed in class, mirages form as light passes through layers of air having different densities. A ray of light will be bent upward when warm air is found below cold air, forming an inferior mirage. The radius of curvature for the ray path (positive for concave up) is given by:
where T is temperature, P is pressure, TSTP = 15ºC, PSTP = 1013.25 hPa, a = 0.0342 K m-1, a is the angle of the ray above horizontal, and nnsp > 1.
a. At least how quickly must the temperature decrease with height to produce an inferior mirage. Note that for an inferior mirage, the ray path must bend upward, or Rc > 0.
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17 ก.ย. 50 16:05:19
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