Two spectators, one nearsighted and one farsighted, take turns looking at the stage through the same theater binoculars. Which of them has to move the binocular tube further apart, if in both cases the image is viewed from the distance of best vision? Calculate the change in the length of the binocular tube when passing it from one viewer to another, if the focal length of the eyepiece (diverging lens) is F = -4 cm, and the distances of best vision for nearsighted and farsighted viewers are d1 = 20 cm and d2 = 50 cm.

Detailed solution. Format gif