1.20 The contrast of an object against its surroundings is defined by C = (B-Bo)/Bo, where B represents the brightness of the object. B = Bo when x , and B = 0 when x = 0, where x denotes the distance between the object and the observer. For the normal eye, the threshold contrast has a value of 0.02. As- suming that the extinction coefficient e is independent of the wavelength in the visible, show that the visual range or visibility is given by x = 3.912/Be. If extinction coefficients for a clear atmosphere containing a background aerosol and for a dense fog are 0.08 and 100 km-, respectively, what would be the visibilities in these cases?