Search results
Results from the WOW.Com Content Network
A Fresnel lens ( / ˈfreɪnɛl, - nəl / FRAY-nel, -nəl; / ˈfrɛnɛl, - əl / FREN-el, -əl; or / freɪˈnɛl / fray-NEL[ 1]) is a type of composite compact lens which reduces the amount of material required compared to a conventional lens by dividing the lens into a set of concentric annular sections.
A zone plate is a device used to focus light or other things exhibiting wave character. [ 1] Unlike lenses or curved mirrors, zone plates use diffraction instead of refraction or reflection. Based on analysis by French physicist Augustin-Jean Fresnel, they are sometimes called Fresnel zone plates in his honor.
Lenticular printing is a technology in which lenticular lenses (a technology also used for 3D displays) are used to produce printed images with an illusion of depth, or the ability to change or move as they are viewed from different angles. Examples include flip and animation effects such as winking eyes, and modern advertising graphics whose ...
The original light was an Argand-Lewis parabolic reflector, lit with candles and with a visibility of 2 miles (3.2 km). Augustin Fresnel invented a superior way of focusing light in the early 1850s and most lighthouses in the U.S. were converted to the Fresnel Lens, with Pemaquid Point receiving a fourth order Fresnel in 1856.
On May 15, 1874, the Gay Head Light was changed from flashing white to "three whites and one red" to differentiate the light from the area's two other principal lights located at Sankaty Head and Montauk Point. All three lights had Fresnel lenses, however, the Gay Head Light was the only light of the 1st Order.
The simplest Fresnel zone plate antenna is the circular half-wave zone plate invented in the nineteenth century. The basic idea is to divide a plane aperture into circular zones with respect to a chosen focal point on the basis that all radiation from each zone arrives at the focal point in phase within ±π/2 range.
The new all-white lighthouse tower was completed in 1868, receiving a first-order Fresnel lens made by Henry-Lepaute and Company of Paris, France that was first lit on May 10, 1868. [ 1 ] [ 6 ] The lower three levels of the tower served as the living quarters for the keepers and his assistants complete with kitchen, living room and bedrooms.
A floral diagram is a schematic cross-section through a young flower. [ 1] It may be also defined as “projection of the flower perpendicular to its axis”. [ 3] It usually shows the number of floral parts, [ Note 2] their sizes, relative positions and fusion. Different organs are represented by distinguishable symbols, which may be uniform ...