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The free-fall time is the characteristic time that would take a body to collapse under its own gravitational attraction, if no other forces existed to ... more

In orbital mechanics, Kepler’s equation relates various geometric properties of the orbit of a body subject to a central force.

It was first ... more

Aperture is a “hole” or an opening through which light travels. The aperture of an optical system is the opening that determines the cone angle ... more

The depth of focus (or depth of field) is a lens optics concept that measures the tolerance of placement of the image plane (the film plane in a camera) in ... more

Eccentricity e of the cylindric section and semi-major axis of the cylindric section depend on the radius of the cylinder and the angle between the secant ... more

The elliptic paraboloid is shaped like an oval cup and can have a maximum or minimum point. In a suitable coordinate system with three axes x, y, and z, it ... more

In optics, particularly as it relates to film and photography, depth of field (DOF) is the distance between the nearest and ... more

Optical magnification is the ratio between the apparent size of an object (or its size in an image) and its true size, and thus it is a dimensionless ... more

The depth of focus (or depth of field) is a lens optics concept that measures the tolerance of placement of the image plane (the film plane in a camera) in ... more

Depth of field (DOF), or depth of focus, is the distance between the nearest and farthest objects in a scene that appear ... more