我也觉的选C ， 大家看寂静里面的最后一个问题， 应该是一个题， 应该是选C 的。 One source of error is refraction, the bending of light beams as they pass through air layers of different temperature and pressure.
To reduce refraction errors, the Chinese team carried in sea level to within five to twelve miles of Everest’s summit, decreasing the amount of air that light passed through on its way to their theodolites
回9楼 One source of error is refraction, the bending of light beams as they pass through air layers of different temperature and pressure. Because light traveling. (30) down from a summit passes through many such layers, a surveyor could sight a mirage rather than the peak itself. 定位到这里没有提到空气潮湿是个因素，仅仅说了温度和压力的差异有关
原文：To reduce refraction errors, the Chinese team carried in sea level to within five to twelve miles of Everest’s summit, decreasing the amount of air that light passed through on its way to their theodolites. The Chinese also launched weather balloons near their theodolites to measure atmospheric temperature and pressure changes to better estimate refraction errors
题目It can be inferred from the passage that refraction would be most likely to cause errors in measurements of a mountain’s elevation under which of the following conditions?
C. When theodolites are used relatively far from the mountain peak. 这个通过初中的物理知识。在传播光媒介的密度固定的情况下，距离离珠峰越远，误差应该会越大。（大家可以去证明下，我还没有真正去证明） 记住：这里增加的前提是：在传播光媒介的密度固定的情况下
D. When weather balloons indicate low air temperature and pressure 之所以会发生折射，是因为光进入两种不同密度的媒介 误差的测量估算（估算的目的貌似是后面会根据误差大小进行调和），需要知道两种不同媒介的密度相对大小（不同高度的大气层的密度是不同的，就把它看做不同的媒介吧） 根据常识大气的密度可以通过温度和气压来测试，好像有个啥公式吧。（具体忘了）
在题目中The Chinese also launched weather balloons near their theodolites to measure atmospheric temperature and pressure changes to better estimate refraction errors 中国的科学家们launched weather balloons 也就是要知道 theodolites 附近大气的温度和气压。也就是要知道媒介的密度。 如果测量出来上面的气压低，温度低。那么上面空气相对地面的密度就会偏小。发生的折射角就会越大。
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发表于 2012-3-11 16:21:06
