[填空题]
A laser beam is directed at thunk 0 *nv(zsr 4/w; (doyz2owvoj;j i+f sw mfvqir/-, 6zw,ql:bm/a2e Moon, 380,000 km from Earth. The beam diverges at an angl j/2l6iw -zfj+, ;fmrs/ qwvmqi: boa,e $\theta$ (Fig. 8–37) of $1.4\times10^{-5}$ rad What diameter spot will it make on the Moon? m