For the present purposes, the light from a star can be treated as a practically collimated beam, but apart from this, a collimated beam is rarely if ever found in nature, though artificially produced beams can be very nearly collimated.
32.
For a thin lens in air, the focal length is the distance from the center of the concave lens ), the focal length is negative, and is the distance to the point from which a collimated beam appears to be diverging after passing through the lens.
33.
The spot size is approximately " f " ? / " D ", where " f " is the focal length of the lens, ? is the wavelength of the light, and " D " is the diameter of the collimated beam incident upon the lens.
34.
An interferometry technique entitled moir?deflectometry [ 1 ], in which the object to be tested ( either phase object or secular surface ) is mounted in the course of a collimated beam followed by a pair of transmission gratings placed at a distance from each other.
35.
For the present purposes, the light from a star, and for some particular purposes, the light of the sun, can be treated as a practically collimated beam, but apart from this, a collimated beam is rarely if ever found in nature, though artificially produced beams can be very nearly collimated.
36.
For the present purposes, the light from a star, and for some particular purposes, the light of the sun, can be treated as a practically collimated beam, but apart from this, a collimated beam is rarely if ever found in nature, though artificially produced beams can be very nearly collimated.
