Answer:
p = 4/3 f
Explanation:
The constructor station describes the position of the image object in relation to the focal length
1 / f = 1 / p + 1 / q
where f is the focal length, p and q are the distances to the object and the image respectively
the objent distance is
1 / p = 1 / f - 1 / q
they indicate that the image is located at q = 4f this distance is positive because the image is after the lens
1 / p = 1 / f - 1 / 4f
1 / p = 3 / 4f
p = 4f / 3
the object is positive because it is to the left of the lens, according to the optical sign convention
The sign convention is that the distance to the objects is positive if it is on the left side of the lens and the image is positive if it is on the right side of the lens.
