The pinhole camera of the figure images distant objects by allowing only a narrow bundle of light rays to pass through thehole and strike the film. If light consisted of particles, you could make the image sharper by making the aperture smaller and smaller. In practice, diffraction of light by the circular aperture limits the maximum sharpness that can be obtained. Consider two distant points of light, such as two distant streetlights. Each will produce a circular diffraction pattern on the film. The two images can justbarely be resolved if the central maximum of one image falls on the first dark fringe of the other image.
A. Optimum sharpness of one image occurs when the diameter ofthe central maximum equals the diameter of the pinhole. What is theoptimum hole size for a pinhole camera in which the filmis 20 cm behind the hole? Assume λ = 550 nm, an average value forvisible light.
B. For this hole size, what is the angle α (in degrees) between two distant sources that can barely be resolved?
C. What is the distance between two streetlights 1 km away that can barely be resolved?
