This intense heat they project in a parallel beam against any object they choose, by means of a polished parabolic mirror of unknown composition, much as the mirror of a lighthouse projects a beam of light.

VOA: special.2010.09.01

So this gives you a little bit of an idea of just how many individual photons there are in a laser beam of light. This is a huge number of photons.

这个给你们一点思路关于,一个激光束有多少独立的光子,这是一个巨大的光子数目。

麻省理工公开课 - 化学原理课程节选

So what we end up with for the number of photons in this laser beam of light is 2.1 times 10 to the 17 photons.

这个激光束的数目是,2，1乘以10的17次方。

麻省理工公开课 - 化学原理课程节选