1. One source of error is refraction, the bending of light beams as they pass through air layers of different temperature and pressure. 误差的一个来源是折射，即光束通过不同温度和压力的空气层时发生的弯曲现象。
2. The Chinese also launched weather balloons near their theodolites to measure atmospheric temperature and pressure changes to better estimate refraction errors. 中国还在经纬仪附近发射了气象气球来测量大气温度和压力变化，以更好地估计折射误差。
3. Refraction of light gives the above results. 光的折射会产生上述的结果。
4. Refraction has been dealt with on page 156 . 折射已经在前面156页谈过。
5. What would a negative index of refraction look like? 如果折射率是负的,会发生什么事情?
