Weather-Ready Nation; Cooperative Observers; Daily Briefing; Damage/Fatality/Injury Statistics; Forecast Models; GIS Data Portal; NOAA Weather Radio; Publications; SKYWARN Storm Spotters; StormReady; TsunamiReady; EDUCATION . Be A Force of Nature; NWS Education Home; NEWS . NWS News; Events; Social Media; Pubs/Brochures/Booklets ; NWS Media Contacts; SEARCH
The gradient is a fancy word for derivative, or the rate of change of a function. Itâs a vector (a direction to move) that. 1  Points in the direction of greatest increase of a function (intuition on why)  Is zero at a local maximum or local minimum (because there is no single direction of increase)
The lens focuses light in the same way as a conventional lens. Gradient-index (GRIN) optics is the branch of optics covering optical effects produced by a gradual variation of the refractive index of a material. Such variations can be used to produce lenses with flat surfaces, or lenses that do not have the aberrations typical of traditional spherical lenses.