Wave

In physics, a wave is an oscillation accompanied by a transfer of energy that travels through space or mass. Frequency refers to the addition of time. Wave motion transfers energy from one point to another, which displace particles of the transmission medium—that is, with little or no associated mass transport. Waves consist, instead, of oscillations or vibrations (of a physical quantity), around almost fixed locations.

There are two main types of waves. Mechanical waves propagate through a medium, and the substance of this medium is deformed. The deformation reverses itself owing to restoring forces resulting from its deformation. For example, sound waves propagate via air molecules colliding with their neighbors. When air molecules collide, they also bounce away from each other (a restoring force). This keeps the molecules from continuing to travel in the direction of the wave.

The second main type of wave, electromagnetic waves, do not require a medium. Instead, they consist of periodic oscillations of electrical and magnetic fields originally generated by charged particles, and can therefore travel through a vacuum. These types of waves vary in wavelength, and include radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.

Silver

Silver is the metallic element with the atomic number 47. Its symbol is Ag, from the Latin argentum, from a PIE root reconstructed as *h₂erǵ-, "grey" or "shining". A soft, white, lustrous transition metal, it possesses the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. The metal occurs naturally in its pure, free form (native silver), as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite. Most silver is produced as a byproduct of copper, gold, lead, and zinc refining.

Silver has long been valued as a precious metal. More abundant than gold, silver metal has functioned in many premodern monetary systems as coinable specie, sometimes even alongside gold. Its purity is typically measured on a per-mille basis; a 94%-pure alloy is described as "0.940 fine". In addition, silver has numerous applications beyond currency, such as in solar panels, water filtration, jewelry and ornaments, high-value tableware and utensils (hence the term silverware), and also as an investment in the forms of coins and bullion. Silver is used industrially in electrical contacts and conductors, in specialized mirrors, window coatings and in catalysis of chemical reactions. Its compounds are used in photographic film and X-rays. Dilute silver nitrate solutions and other silver compounds are used as disinfectants and microbiocides (oligodynamic effect), added to bandages and wound-dressings, catheters and other medical instruments.

Oenothera

Oenothera is a genus of about 145 species of herbaceous flowering plants native to the Americas. It is the type genus of the family Onagraceae. Common names include evening primrose, suncups, and sundrops. They are not closely related to the true primroses (genus Primula).

Description

The species vary in size from small alpine plants 10 centimeters tall, such as O. acaulis from Chile, to vigorous lowland species growing to 3 meters, such as O. stubbei from Mexico. The leaves form a basal rosette at ground level and spiral up to the flowering stems. The blades are dentate or deeply lobed (pinnatifid). The flowers of many species open in the evening, hence the name "evening primrose". They may open in under a minute. Most species have yellow flowers, but some have white, purple, pink, or red. Most native desert species are white. Oenothera caespitosa, a species of western North America, produces white flowers that turn pink with age. One of the most distinctive features of the flower is the stigma, which has four branches in an X shape.