Furthermore, the result of the device performance may be affected by the locations of the observer because the lights which the observer received are not always parallel rays
. We use a point receiver to represent the observer and calculate the light traces with the point receiver placed at different locations.
"It is most intense when focused on a single point rather than beamed in parallel rays
. But a laser that focuses less sharply, in more of a long X shape rather than a short X shape, could still do the business.
Two parallel rays
from the top and bottom of the object are refracted at the front surface of the eye, cross a short distance behind its geometrical centre, at a point referred to by Gaukroger as the focus, and then diverge again to produce an inverted image on the retina.
Previous analyzers could resolve only a very intense X-ray beam, a beam of a single wavelength, or a beam of highly parallel rays
. Coauthor Timm Weitkamp of the European Synchrotron Radiation Facility in Grenoble, France, says the new gratings can handle the less intense, multiwavelength, and multidirectional beams that emerge from typical hospital X-ray tubes.
In a flat universe, parallel rays
stay parallel forever on the largest scales.
South of Mare Crisium in Mare Fecunditatis are two small craters with unique parallel rays
streaming from one of them.