Light, visible light, or visible radiation is electromagnetic radiation that can be perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terahertz. The visible band sits adjacent to the infrared (with longer wavelengths and lower frequencies) and the ultraviolet (with shorter wavelengths and higher frequencies), called collectively optical radiation.
In physics, the term "light" may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. The primary properties of light are intensity, propagation direction, frequency or wavelength spectrum, and polarization. Its speed in vacuum, 299792458 m/s, is one of the fundamental constants of nature. All electromagnetic radiation exhibits some properties of both particles and waves. Single, massless elementary particles, or quanta, of light called photons can be detected with specialized equipment; phenomena like interference are described by waves. Most everyday interactions with light can be understood using geometrical optics; quantum optics, is an important research area in modern physics.
The main source of natural light on Earth is the Sun. Historically, another important source of light for humans has been fire, from ancient campfires to modern kerosene lamps. With the development of electric lights and power systems, electric lighting has effectively replaced firelight.
Multi is a shortened form of "multiple". It may refer to:
- Alternate character, in online gaming
- Multi two diamonds, a contract bridge convention
- Multirhyme, a synonym for feminine rhyme used in hip hop music
- Multi (To Heart), a character from the visual novel and anime series To Heart
- Multi-touch display
Purpose is the end for which something is done, created or for which it exists. Purpose is an abiding intention to achieve a long-term goal that is both personally meaningful and makes a positive mark on the world. It is part of the topic of intentionality and goal-seeking behavior.
Related concepts and subjects:
- Goal, a desired result or possible outcome
- Intention, the state of intending something or the action intended
- Motivation, a driving factor for actions, willingness, and goals
- Determination or resolve
- Meaningful life — a life of purpose
- Purpose clause, in grammar a dependent adverbial clause expressing purpose
- Purpose of life, questions regarding the significance of living or existence in general
- Teleology, the philosophical attempt to describe things in terms of their apparent purpose or goal
- Teleonomy, the apparent purposefulness of structures and functions in living organisms
With or WITH may refer to:
- With, a preposition in English
- Carl Johannes With (1877–1923), Danish doctor and arachnologist
- With (character), a character in D. N. Angel
- With (novel), a novel by Donald Harrington
- With (album), a 2014 album by TVXQ
- With (EP), a 2021 EP by Nam Woo-hyun
Work may refer to:
- Work (human activity), intentional activity people perform to support themselves, others, or the community
- Manual labour, physical work done by humans
- House work, housework, or homemaking
- Working animal, an animal trained by humans to perform tasks
- Work (physics), the product of force and displacement
- Work (electric field), the work done on a charged particle by an electric field
- Work (thermodynamics), energy transferred by the system to its surroundings
- Creative work, a manifestation of creative effort
- Work of art, an artistic creation of aesthetic value
- Career, an individual's journey through learning, work and other aspects of life
- Employment, a relationship between two parties where work is paid for
A workbench is a sturdy table at which manual work is done. They range from simple flat surfaces to very complex designs that may be considered tools in themselves. Workbenches vary in size from tiny jewellers benches to the huge benches used by staircase makers. Almost all workbenches are rectangular in shape, often using the surface, corners and edges as flat/square and dimension standards. Design is as varied as the type of work for which the benches are used but most share these attributes:
- A comfortable height for working with provisions for seated or standing work
- A way to fix the workpiece to the surface so that it may be worked with both hands
- Provisions for mounting, storing and accessing tools
Workbenches are made from many different materials including metal, wood, stone, and composites depending on the needs of the work.
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