At what distance from the diffusing lens should the object be placed to obtain a ghost image

At what distance from the diffusing lens should the object be placed to obtain a ghost image at a distance of 0.25. the focal length of the lens is -0.5.

Quite simply, lens tasks are typical. Since, according to the condition of the problem, a diffusing lens is given, we take the formula: -1 / F = 1 / d-1 / f. To make it a little clearer, we first express 1 / d: 1 / d = 1 / f-1 / F. Let’s substitute and calculate: 1 / 0.25 -1 / 0.5 = 2. We found that the ratio 1 / d = 2, now we express d, it will be equal to the inverse ratio: 1/2. This means that the distance at which you need to leave the object is 0.5 (m).