Resolving Power: a Camera Used for Aerial Surveillance Has a Lens

Multiple Choice

Resolving power: A camera used for aerial surveillance has a lens with a 30-cm maximum aperture and a 42-cm focal length. Assume light of 550-nm wavelength is used and that the resolution of the camera is limited solely by diffraction. What is the angular resolution of the camera at maximum aperture?

A) 1.6 µrad
B) 2.2 µrad
C) 3.2 µrad
D) 4.5 µrad
E) 6.3 µrad