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Oct 4, 2012 · Once there, the photons stream out, illuminating Earth, the solar system and beyond. The number released from the surface every second is so vast that it is more than a billion billion times greater than the number of grains of sand on our planet.
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Once there, the photons stream out, illuminating Earth, the...
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- 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.
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.
The Sun is the major source of light for the earth. The sun is a massive ball of fire, at the centre of which nuclear fusion produces massive energy. This energy comes out as heat and light.
- There are countless sources of light, but they can all be categorised under either of the two following categories- Natural sources Artificial sou...
- When certain objects are heated to a high temperature, they begin to emit light. Both infrared and visible light is produced in the process. Examp...
- The change in direction of a wave, while passing from one medium to another is known as refraction.
- Light is a form of energy that enables us to see things. Light starts from a source and bounces off objects which are perceived by our eyes and our...
- Twinkling of stars and formation of rainbow.
Aug 12, 2015 · Far away from the glow of civilization, we humans can survey thousands of tiny pinpricks of light. But how? Where does that light come from? How does it make its way to us?
Mar 13, 2018 · When light travels through space from the sun, all of the frequencies of light travel in a straight line. When light hits the atmosphere, however, the photons begin to collide with gas molecules. Red, orange and yellow photons have long wavelengths and can travel right through the gas molecules.
Origin of Light. Scientists today accept the existence of photons and their weird wave-particle behavior. What they still debate is the more existential side of things, such as where light came from in the first place.
