[填空题]
A laser beam is direcs 3jmpo3r8fh)+k:gxeted at the Moon, 380,000 km from Earth. The beam div- a9o:ism jb5 nmre.6yerges at an angmnm5j:6- b e or9a.isyle $\theta$ (Fig. 8–37) of $1.4\times10^{-5}$ rad What diameter spot will it make on the Moon? m