grandissement

Grandissement, in the context of optics and geometry, refers to the ratio of the size of an image to the size of the original object. This ratio is typically expressed as a dimensionless quantity. A grandissement greater than one indicates that the image is larger than the object, while a grandissement less than one signifies that the image is smaller. A grandissement of exactly one means the image and object are the same size.

In optical instruments like microscopes and telescopes, grandissement is a crucial parameter that determines how much closer an object appears to the observer. For a simple magnifying glass, the linear grandissement is often approximated by 1 + (250 mm / f), where f is the focal length of the lens in millimeters, and 250 mm is taken as the conventional near point of distinct vision.

In geometrical transformations, grandissement is a similarity transformation that scales an object from a fixed point. This scaling factor is the grandissement. This type of transformation preserves angles and the shape of objects, only changing their size and possibly their orientation relative to the fixed point. The concept is fundamental in understanding how shapes change proportionally.