Question

A spy camera is said to be able to read the numbers on a car's license plate. If the numbers on the plate are 6.0 cm apart, and the spy satellite is at an altitude of 160 km, what must be the diameter of the camera's aperture? (Assume light with a wavelength of 600 nm.)

Answer 1

To be able to resolve 6cm the lens would be ~3.905m (Diffraction limited ground sample distance= 2.44 * wavelength * altitude / aperture (diameter) of lens.