Refraction of light at the interface between two media of different refractive indices, with n₂ > n₁. Since the phase velocity is lower in the second medium (v₂ < v₁), the angle of refraction θ₂ is less than the angle of incidence θ₁; that is, the ray in the higher-index medium is closer to the normal.

The straw seems to be broken, due to refraction of light as it emerges into the air.

Refraction is the change in direction of a wave due to a change in its speed. A wave is a disturbance that propagates through Space and Time, usually with transference of Energy. Speed is the rate of motion, or equivalently the rate of change in position often expressed as Distance d traveled per unit of This is most commonly seen when a wave passes from one medium to another. An optical medium is material through which Electromagnetic waves propagate Refraction of light is the most commonly seen example, but any type of wave can refract when it interacts with a medium, for example when sound waves pass from one medium into another or when water waves move into water of a different depth. Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 An acoustic wave is a weak compression wave (meaning a small pressure change that moves at the Speed of sound. Refraction is described by Snell's law, which states that the angle of incidence is related to the angle of refraction by

or

where

v₁ and v₂ are the wave velocities through the respective media. In Optics and Physics, Snell's law (also known as Descartes' law or the law of refraction) is a formula used to describe the relationship

θ₁ and θ₂ are the angles between the normal (to the interface) plane and the incident waves respectively.

n₁ and n₂ are the refractive indices

Explanation

In optics, refraction occurs when light waves travel from a medium with a given refractive index to a medium with another. Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium At the boundary between the media, the wave's phase velocity is altered, it changes direction, and its wavelength increases or decreases but its frequency remains constant. The phase velocity (or phase speed) of a Wave is the rate at which the phase of the wave propagates in space In Physics wavelength is the distance between repeating units of a propagating Wave of a given Frequency. Frequency is a measure of the number of occurrences of a repeating event per unit Time. For example, a light ray will refract as it enters and leaves glass; understanding of this concept led to the invention of lenses and the refracting telescope

Refraction of light waves in water. In Optics, a ray is an idealized narrow Beam of light. Rays are used to model the propagation of Light through an optical system by dividing the real light Glass in the common sense refers to a Hard, Brittle, transparent Solid, such as that used for Windows many An invention is a new form composition of matter device or Process. A lens is an optical device with perfect or approximate Axial symmetry which transmits and refracts Light, converging or diverging A refracting or refractor telescope is a dioptric Telescope that uses a lens as its objective to form an image The dark rectangle represents the actual position of a pencil sitting in a bowl of water. The light rectangle represents the apparent position of the pencil. Notice that the end (X) looks like it is at (Y), a position that is considerably shallower than (X).

Photograph of refraction of waves in a ripple tank

Refraction can be seen when looking into a bowl of water. In Physics and Engineering, a ripple tank is a shallow glass tank of water used in schools and colleges to demonstrate the basic properties of Waves It Air has a refractive index of about 1. 0003, and water has a refractive index of about 1. 33. If a person looks at a straight object, such as a pencil or straw, which is placed at a slant, partially in the water, the object appears to bend at the water's surface. This is due to the bending of light rays as they move from the water to the air. Once the rays reach the eye, the eye traces them back as straight lines (lines of sight). The lines of sight (shown as dashed lines) intersect at a higher position than where the actual rays originated. This causes the pencil to appear higher and the water to appear shallower than it really is. The depth that the water appears to be when viewed from above is known as the apparent depth. This is an important consideration for spearfishing from the surface because it will make the target fish appear to be in a different place, and the fisher must aim lower to catch the fish. Spearfisherman redirects here For the former diving gear company see Spearfisherman (company.

Diagram of refraction of water waves

The diagram on the right shows an example of refraction in water waves. Ocean surface waves are Surface waves that occur on the Free surface of the Ocean. Ripples travel from the left and pass over a shallower region inclined at an angle to the wavefront. The waves travel more slowly in the shallower water, so the wavelength decreases and the wave bends at the boundary. The dotted line represents the normal to the boundary. The dashed line represents the original direction of the waves. The phenomenon explains why waves on a shoreline never hit the shoreline at an angle. Whichever direction the waves travel in deep water, they always refract towards the normal as they enter the shallower water near the beach.

Refraction is also responsible for rainbows and for the splitting of white light into a rainbow-spectrum as it passes through a glass prism. A rainbow is an optical and meteorological phenomenon that causes a spectrum of Light to appear in the Sky when the Sun In Optics, a dispersive prism is a type of optical prism, normally having the shape of a geometrical triangular prism. Glass has a higher refractive index than air and the different frequencies of light travel at different speeds (dispersion), causing them to be refracted at different angles, so that you can see them. In Optics, dispersion is the phenomenon in which the Phase velocity of a wave depends on its frequency The different frequencies correspond to different colors observed.

While refraction allows for beautiful phenomena such as rainbows, it may also produce peculiar optical phenomena, such as mirages and Fata Morgana. An optical phenomenon is any observable event which results from the interaction of Light and Matter. A mirage is a naturally-occurring Optical phenomenon, in which light rays are bent to produce a displaced image of distant objects or the sky A fata morgana is a Mirage, an Optical phenomenon which results from a Temperature inversion. These are caused by the change of the refractive index of air with temperature.

Refraction in a Perspex (acrylic) block. Poly(methyl methacrylate ( PMMA) or poly(methyl 2-methylpropenoate is a Thermoplastic and transparent Plastic.

Snell's law is used to calculate the degree to which light is refracted when traveling from one medium to another. In Optics and Physics, Snell's law (also known as Descartes' law or the law of refraction) is a formula used to describe the relationship

Recently some metamaterials have been created which have a negative refractive index. A metamaterial (or meta material) is a material which gains its properties from its structure rather than directly from its composition A metamaterial (or meta material) is a material which gains its properties from its structure rather than directly from its composition With metamaterials, we can also obtain the total refraction phenomena when the wave impedances of the two media are matched. Total refraction occurs when an incident wave on an interface between two media with opposite Refractive index signs is completely transmitted. There is no reflected wave.

Also, since refraction can make objects appear closer than they are, it is responsible for allowing water to magnify objects. First, as light is entering a drop of water, it slows down. If the water's surface is not flat, then the light will be bent into a new path. This round shape will bend the light outwards and as it spreads out, the image you see gets larger.

A useful analogy in explaining the refraction of light would be to imagine a marching band as they march from pavement (a fast medium) into mud (a slower medium) The marchers on the side that runs into the mud first will slow down first. This causes the whole band to pivot slightly toward the normal (make a smaller angle from the normal).

Optometry

Acoustics

In underwater acoustics, refraction is the bending or curving of a sound ray that results when the ray passes through a sound speed gradient from a region of one sound speed to a region of a different speed. Underwater acoustics is the study of the propagation of Sound in Water and the interaction of the mechanical waves that constitute sound with the water and its boundaries In Acoustics, the sound speed gradient is the rate of change of the Speed of sound with distance for example with depth in the Ocean,or height in the The amount of ray bending is dependent upon the amount of difference between sound speeds, that is, the variation in temperature, salinity, and pressure of the water. ^[2] Similar acoustics effects are also found in the Earth's atmosphere. Acoustics is the interdisciplinary science that deals with the study of Sound, Ultrasound and Infrasound (all mechanical waves in gases liquids and solids Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five The phenomenon of refraction of sound in the atmosphere has been known for centuries;^[3] however, beginning in the early 1970s, widespread analysis of this effect came into vogue through the designing of urban highways and noise barriers to address the meteorological effects of bending of sound rays in the lower atmosphere. * * * * * * * * * * * * * * * * * * * * * * Before adding any more images to this * * page please do carefully consider * * whether they would be mere decoration * * or actually improve A noise barrier (also called a soundwall, sound berm, sound barrier, or acoustical barrier) is an exterior structure designed to protect Meteorology (from Greek grc μετέωρος metéōros, "high in the sky" and grc -λογία -logia) is the Interdisciplinary ^[4]

See also

In this extreme example, refraction causes the Golden Gate Bridge to appear upside-down in the raindrops. The Golden Gate Bridge is a suspension Bridge spanning the Golden Gate, the opening of the San Francisco Bay onto the Pacific Ocean

• Birefringence (Double refraction)
• Diffraction
• Huygens-Fresnel principle
• List of indices of refraction
• Reflection
• Snell's law
• Total internal reflection
• Total refraction
• Willebrord Snellius

Reference

1. ^ Eye Glossary. Birefringence, or double refraction, is the decomposition of a ray of Light into two rays (the ordinary ray and the extraordinary ray Diffraction is normally taken to refer to various phenomena which occur when a wave encounters an obstacle The Huygens–Fresnel principle (named for Dutch Physicist Christiaan Huygens, and French physicist Augustin-Jean Fresnel Reflection is the change in direction of a Wave front at an interface between two different media so that the wave front returns into the medium from which In Optics and Physics, Snell's law (also known as Descartes' law or the law of refraction) is a formula used to describe the relationship Total refraction occurs when an incident wave on an interface between two media with opposite Refractive index signs is completely transmitted. “Snellius” redirects here For the lunar crater named Snellius see Snellius (crater. Retrieved on 2006-05-23. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 1430 - Siege of Compiègne: Joan of Arc is captured by the Burgundians while leading an army to relieve Compiègne
2. ^ (August 2006) Navy Supplement to the DOD Dictionary of Military and Associated Terms. Department Of The Navy. NTRP 1-02.  
3. ^ Mary Somerville, On the Connexion of the Physical Sciences, J. Murray Publishers, (originally by Harvard University), 499 pages (1840)
4. ^ [1] C. Michael Hogan, Analysis of highway noise, Journal Water, Air, & Soil Pollution, Publisher Springer Netherlands, ISSN 0049-6979, Volume 2, Number 3, Pages 387-392, September, 1973

External links

• Java explanatory animation
• Java illustration of refraction
• Java simulation of refraction through a prism
• Reflections and Refractions in Ray Tracing, a simple but thorough discussion of the mathematics behind refraction and reflection.