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Light is called an 'electromagnetic wave' for historical reasons* in the following sense: It turned out that the effects of visible light and other radiation can be calculated using Maxwell's equations, which are also used to model the behaviour of electrically charged particles. This was an instant of a successful unification and it hasn't been dismissed since.
- 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.
In physics, the term "light" may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not. [4][5] 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.
Dec 7, 2022 · Light has the properties of waves. Like ocean waves, light waves have crests and troughs. The distance between one crest and the next, which is the same as the distance between one trough and the next, is called the wavelength. The frequency of a wave is the number of crests (or troughs) that pass a point in one second.
Light is an electromagnetic wave made up of little packets of energy called photons. Light is indispensable in our life. Without light we cannot imagine life on Earth. Our day-to-day activities would be inefficient and life would probably be boring in a world without light. So, we cannot take light lightly.
Light is produced when an electron in an atom drops to a lower energy level, releasing the energy as a photon. Quantum physics tells us that atomic electrons can only have certain fixed levels of energy, so that when an electron drops to a lower level it will emit a predictable amount or ‘quantum’ of energy. The further the electron drops ...
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Why is light called an 'electromagnetic wave'?
Is light a particle or a wave?
Is visible light a form of electromagnetic radiation?
What is a ray in physics?
What are the properties of light waves?
What are the properties of light in physics?
Light can be described both as a wave and as a particle. There are two experiments in particular that have revealed the dual nature of light. When we’re thinking of light as being made of particles, these particles are called “photons”. Photons have no mass, and each one carries a specific amount of energy.
