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- Light travels as waves. These are transverse waves, like ripples in water.
Oct 4, 2024 · Light sources are a type of particle accelerator that produce powerful beams of X-rays, ultra-violet, or infrared light. These beams are similar to how holding an envelope in front of a bright light can reveal something about what’s inside the envelope.
For example, fireflies produce light by this means and boats moving through water can disturb plankton which produce a glowing wake. Certain substances produce light when they are illuminated by more energetic radiation, a process known as fluorescence .
Light is electromagnetic radiation. A particular frequency of this radiation (around 390-700 nm) is visible to the human eye. Everything that we see around us is because of light. Light is a form of energy and like all energies, it is produced from a source. In Physics, these are called light sources.
- 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.
- 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 is a transverse, electromagnetic wave that can be seen by the typical human. The wave nature of light was first illustrated through experiments on diffraction and interference. Like all electromagnetic waves, light can travel through a vacuum. The transverse nature of light can be demonstrated through polarization.
Light is a form of energy produced by a light source. Light is made of photons that travel very fast. Photons of light behave like both waves and particles. Light sources. Something that produces light is called a light source. There are two main kinds of light sources: Incandescent sources use heat to produce light.
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The light of such objects is incandescent. Other light sources emit light energy but no heat energy. They are known as luminescent, or cold light, sources. Neon and fluorescent lights are luminescent. Measuring Light. The total amount of light given off by a light source is called the luminous flux. It is measured in units called lumens.
