One way to get round this limitation is to set up a laser in mid-air, its beam sampling the molecules along its path as it returns to the source.

避免这个局限的一种方法是在两者之间放置一个激光器，它的光束在返回光源时对途径的分子进行取样。

youdao

Graham said that, if someone walked through the beam, it would shut down within a thousandth of a second, then restart once the path was clear.

Graham说，一旦有人穿越光束，它会在千分之一秒内关闭，并在路径无障后即刻重启。

youdao

When an accelerator is used to treat tumour of illness, the distribution of doses is changed by commonly inserting a wedge into the path of radial beam.

利用加速器治疗肿瘤时，通常要在射线束的路径上加入楔形板以改变平野的剂量分布。

youdao

This exploits one of the predictions of Einstein's general theory of relativity: that the path of a beam of light (which is a straight line in empty space) is bent inwards by the gravity of a massive object.

ECONOMIST: Cosmology: I spy with my little gravitational lens | The

Walk along a wooded path and the Nao diffuses and dims its beam to give you a more expansive view of the terrain.

WSJ: The Petzl Nao: A Smarter Light | At Play

Many Greyhound buses sweep the road ahead with a radar beam, which warns the driver if there is an obstacle in his path.

ECONOMIST: A safety bet