[填空题]
Spy planes fly at extremely high alm b 0uq swcsf7p.ih:wg1.l7:stcc c ;h/lfi)-titudes (25 $km$) to avoid interception. Their cameras are reportedly able to discern features as small as 5 $cm$. What must be the minimum aperture of the camera lens to afford this resolution? (Use $\lambda=550\mathrm{~nm}.$)D = cm
