[填空题]
Estimate the angular spread of a laserl:yytcj5n.q .scfm) 7 9x9 qnj beam due to diffraction if(xrt,g uwrjcw:;wz4/a +/f n: txfol+a-ysy5 the beam emerges through r:sjf ot,+:rwxw-yn( z ;5 wglaayc+/ u4tx /fa $3.0$-mm-diameter mirror. Assume that $\lambda = 694 \, \text{nm}$. What would be the diameter of this beam if it struck
$\theta$ = $ \times 10^{-4}\ \text{rad}$
(a) a satellite $300 \, \text{km}$ above the Earth, D = $ \times 10^{2}\ \text{m}$
(b) the Moon?D = $ \times 10^{5}\ \text{m}$
