The focal length of the collecting lens is 20 cm. At what distance from the lens should the object

The focal length of the collecting lens is 20 cm. At what distance from the lens should the object be placed to make its image in full size?

To find the distance at which an object is required to be placed from a given collecting lens, we use the formula: F = f * d / (f + d) = Г * d * d / (Г * d + d).

Values of variables: F – focal length of a given lens (F = 20 cm = 0.2 m); G – lens magnification (G = 1).

Calculation: F = G * d * d / (G * d + d) = 1 * d * d / (1 * d + d) = d2 / 2d = d / 2 = 0.2.

d = 0.2 * 2 = 0.4 m.

Answer: The object must be placed at a distance of 0.4 m from the given collecting lens.