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Jul 15, 2022 · Radiant Energy. Radiant energy, also called electromagnetic radiation, is the energy emitted by electromagnetic waves that travel through space without any medium. It is the energy that can be seen or felt by every living being, meaning it can be both visible and invisible. The light we see all around us and the warmth we feel when we are out ...
Radiant energy, also known as electromagnetic radiation (EMR), is energy transmitted without the movement of mass. Practically speaking, this is the energy found in electromagnetic waves, also known as light. Light is made of individual particles called photons, each carrying a small "packet" of energy. Because photons are so small, light ...
- Overview
- Ray theories in the ancient world
Light is electromagnetic radiation that can be detected by the human eye. Electromagnetic radiation occurs over an extremely wide range of wavelengths, from gamma rays with wavelengths less than about 1 × 10−11 metres to radio waves measured in metres.
What is the speed of light?
The speed of light in a vacuum is a fundamental physical constant, and the currently accepted value is 299,792,458 metres per second, or about 186,282 miles per second.
What is a rainbow?
A rainbow is formed when sunlight is refracted by spherical water droplets in the atmosphere; two refractions and one reflection, combined with the chromatic dispersion of water, produce the primary arcs of colour.
Why is light important for life on Earth?
While there is clear evidence that simple optical instruments such as plane and curved mirrors and convex lenses were used by a number of early civilizations, ancient Greek philosophers are generally credited with the first formal speculations about the nature of light. The conceptual hurdle of distinguishing the human perception of visual effects from the physical nature of light hampered the development of theories of light. Contemplation of the mechanism of vision dominated these early studies. Pythagoras (c. 500 bce) proposed that sight is caused by visual rays emanating from the eye and striking objects, whereas Empedocles (c. 450 bce) seems to have developed a model of vision in which light was emitted both by objects and the eye. Epicurus (c. 300 bce) believed that light is emitted by sources other than the eye and that vision is produced when light reflects off objects and enters the eye. Euclid (c. 300 bce), in his Optics, presented a law of reflection and discussed the propagation of light rays in straight lines. Ptolemy (c. 100 ce) undertook one of the first quantitative studies of the refraction of light as it passes from one transparent medium to another, tabulating pairs of angles of incidence and transmission for combinations of several media.
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With the decline of the Greco-Roman realm, scientific progress shifted to the Islamic world. In particular, al-Maʾmūn, the seventh ʿAbbāsid caliph of Baghdad, founded the House of Wisdom (Bayt al-Hikma) in 830 ce to translate, study, and improve upon Hellenistic works of science and philosophy. Among the initial scholars were al-Khwārizmī and al-Kindī. Known as the “philosopher of the Arabs,” al-Kindī extended the concept of rectilinearly propagating light rays and discussed the mechanism of vision. By 1000, the Pythagorean model of light had been abandoned, and a ray model, containing the basic conceptual elements of what is now known as geometrical optics, had emerged. In particular, Ibn al-Haytham (Latinized as Alhazen), in Kitab al-manazir (c. 1038; “Optics”), correctly attributed vision to the passive reception of light rays reflected from objects rather than an active emanation of light rays from the eyes. He also studied the mathematical properties of the reflection of light from spherical and parabolic mirrors and drew detailed pictures of the optical components of the human eye. Ibn al-Haytham’s work was translated into Latin in the 13th century and was a motivating influence on the Franciscan friar and natural philosopher Roger Bacon. Bacon studied the propagation of light through simple lenses and is credited as one of the first to have described the use of lenses to correct vision.
Light. Light is technically any form of radiant energy, but is almost always taken to mean visible radiant energy. This visible radiant energy is between 380 nm (a nm is one billionth of a meter) and 750 nm. Figure 1 shows how small a portion of the total spectrum the visible spectrum is. Light is a form of electromagnetic radiation, which ...
radiant energy, energy that is transferred by electromagnetic radiation, such as light, X-rays, gamma rays, and thermal radiation, which may be described in terms of either discrete packets of energy, called photons, or continuous electromagnetic waves. The conservation of energy law requires that the radiant energy absorbed or emitted by a ...
- The Editors of Encyclopaedia Britannica
2. Light radiation can be emitted by a natural source, such as the Sun and other stars, or by an artificial source, such as a light bulb. 3. Light carries energy, which is called luminous energy. This luminous energy is transformed into thermal energy when it comes into contact with a surface. 4. Light is almost instantaneous. It travels at a ...
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Visible light such as sunlight carries radiant energy, which is used in solar power generation. In physics, and in particular as measured by radiometry, radiant energy is the energy of electromagnetic [1] and gravitational radiation. As energy, its SI unit is the joule (J). The quantity of radiant energy may be calculated by integrating radiant ...
