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Refraction is the change in direction of a wave due to a change in its speed. It is essentially a surface phenomenon . The phenomenon is mainly in governance to the law of conservation of energy. The proper explanation would be that due to change of medium, the phase velocity of the wave is changed but its frequency remains constant. This is most commonly observed when a wave passes from one medium to another at any angle other than 90° or 0°. Refraction of light is the most commonly observed phenomenon, 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. Refraction is described by Snell's law, which states that for a given pair of media and a wave with a single frequency, the ratio of the sines of the angle of incidence θ1 and angle of refraction θ2is equivalent to the ratio of phase velocities (v1 / v2) in the two media, or equivalently, to the opposite ratio of the indices of refraction (n2 / n1):
In general, the incident wave is partially refracted and partially reflected; the details of this behavior are described by the Fresnel equations.
Contents[hide]- 1 Explanation
- 2 Clinical significance
- 3 Acoustics
- 4 Gallery
- 5 See also
- 6 References
- 7 External links
In optics, refraction is a phenomenon that often occurs when waves travel from a medium with a given refractive index to a medium with another at an oblique angle. At the boundary between the media, the wave's phase velocity is altered, usually causing a change in direction. Its wavelength increases or decreases but its frequency remains constant. For example, a light ray will refract as it enters and leaves glass, assuming there is a change in refractive index. A ray traveling along the normal (perpendicular to the boundary) will change speed, but not direction. Refraction still occurs in this case. Understanding of this concept led to the invention of lenses and the refracting telescope. An object (in this case a pencil) part immersed in water looks bent due to refraction: the light waves from X change direction and so seem to originate at Y.
Refraction can be seen when looking into a bowl of water. 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. Diagram of refraction of water waves.
The diagram on the right shows an example of refraction in water waves. 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. This phenomenon explains why waves on a shoreline tend to strike the shore close to a perpendicular angle. As the waves travel from deep water into shallower water near the shore, they are refracted from their original direction of travel to an angle more normal to the shoreline.[1] Refraction is also responsible for rainbows and for the splitting of white light into a rainbow-spectrum as it passes through a glass prism. Glass has a higher refractive index than air. When a beam of white light passes from air into a material having an index of refraction that varies with frequency, a phenomenon known as dispersion occurs, in which different coloured components of the white light are refracted at different angles, i.e., they bend by different amounts at the interface, so that they become separated. The different colors correspond to different frequencies.
While refraction allows for beautiful phenomena such as rainbows, it may also produce peculiar optical phenomena, such as mirages and Fata Morgana. These are caused by the change of the refractive index of air with temperature.
Recently some metamaterials have been created which have a negative refractive index. With metamaterials, we can also obtain total refraction phenomena when the wave impedances of the two media are matched. There is then no reflected wave.[2]
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 at an oblique angle 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).
Clinical significanceIn medicine, particularly optometry, ophthalmology and orthoptics, refraction (also known as refractometry) is a clinical test in which a phoropter may be used by the appropriate eye care professional to determine the eye's refractive error and the best corrective lenses to be prescribed. A series of test lenses in graded optical powers or focal lengths are presented to determine which provide the sharpest, clearest vision.[3] AcousticsIn 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. 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.[4] Similar acoustics effects are also found in the Earth's atmosphere. The phenomenon of refraction of sound in the atmosphere has been known for centuries;[5] 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.[6] GalleryRefraction in a Perspex (acrylic) block.The straw appears to be broken, due to refraction of light as it emerges into the air.
Photograph of refraction of waves in a ripple tank.
What else can I help you with?
Why a stick in water seems crooked?
It's because of refraction, the way that light rays move through water.
Why there is a bend in thermometer?
The simple answer: light refract under water thus the image of the ruler is slightly warped due to this effect.The reason light refracts under water is the velocity of light (or any electromagnetic wave in fact) is slower when traveling through a denser medium (it reaches its fastest speed when in a vacuum). Since the light hits the different medium at an angle (or else it wouldn't refract), one side of the wave slows down, thus it bends towards the slower side, for instance imagine you are roller skating on the road, but you put one foot on the lawn, you immediately start turning towards the lawn since the grass slows one side of your body down, its pretty much the same thing with light, it bends toward the slower side.Refraction is modeled by Snell's Law:n1sin(theta1) = n2sin(theta2)where n is the index of refractiontheta is the angle of incidence(the angle measured from the 90 degree mark of the surface)a pencil in water looks bent because of refraction. when light enters a substance with a different density than the one it came out of, the light either slows down or speeds up. this makes the light appear bent. If there is a pencil in the water, it appears bent because the light is traveling at different speeds through water and air.
What causes an object's velocity to change?
A change in velocity is caused by a change in acceleration. Objects do not speed up, slow down, or change direction unless they are pushed in some way. The acceleration (a) of an object with mass (m) produced by a given force (F) may be calculated using the equation a = F/m.
What are the three forces that act on objects without touching them?
We know that gravity, magnetic and electricforces or fields act across distance in a way that only the lines of force impinge on an affected object.
A group of objects wich are related to each other in the same way are said to belong to the same?
category
When light is bent it is called what?
When light is bent, it is called refraction. Refraction occurs when light travels through different mediums, such as air and water, causing it to change speed and direction. This bending of light is responsible for optical phenomena such as rainbows and the way objects appear distorted when submerged in water.
What causes a pencil to look bent in water?
Water can cause a distortion of the light and in turn causes optical illusions. The water refracts light in such a way that objects viewed through light can appear bent, or angled sharply. This is a function of refraction.
Why do objects in water appear different?
Objects in water appear different due to refraction, which occurs as light travels from one medium to another. This causes the light rays to bend, altering the way objects underwater are perceived from above the surface. The refraction can make objects appear larger, closer, or distorted compared to when they are viewed in air.
If you look underwater are things further away or closer than they appear?
When you look underwater, objects appear closer than they actually are due to the refraction of light. The way light moves through water causes objects to appear closer and larger than they really are, which can make judging distance and size more challenging when viewing objects underwater.
What is the main principal of lens?
The main principle of a lens is to refract (bend) light waves in a way that converges or diverges them to create an image. This refraction occurs due to the change in density as light passes through the lens, causing the light rays to bend and focus at a specific point, allowing for magnification or reduction of objects.
Why do things look distorted when you look into a fish bowl?
When you look into a fishbowl or any curved glass container, the light bends as it passes through the curved surface, causing the objects inside to appear distorted or magnified. This distortion is due to the refraction of light at the curved boundary between air and glass, altering the way the objects are perceived by your eyes.
How do you change the way you look to others in Pokemon Diamond?
You can't change the way you look to others in Pokemon Diamond. The avatar that is chosen how you look to others is completely by random, and there is no way to change it.
Why are fish not where they seem to be in a fish tank?
Light hits the glass and water at one angle and leaves at another angle (refraction). So, the light that causes you to see the fish has been interrupted in this way. This is also why fish (and other objects) are not where they seem when you look at them from above and not through glass.
How do you change the way you look at pictures on Facebook?
You change the way to look at pictures by updating your home page.
What are the effects of refraction of light?
The effects of the wave nature of light include the reflection, refraction, dispersion, and diffraction of light, and its behavior during constructive and destructive interference. Everyday examples include: -- Mirrors, which would not work without reflection. -- Eyeglasses and the human eye, which would not work without refraction. -- Satellite dishes, which would not work without constructive interference.
What happens when the objects in the way of the waves move?
When objects in the way of waves move, the waves can be blocked or absorbed by the objects. This can cause the waves to change direction, scatter, or reflect off the moving objects. The movement of the objects can also affect the amplitude and wavelength of the waves.
When light is traveling fast in a medium which way will it bend?
When light travels fast in a medium, it tends to bend away from the normal. This is known as refraction. Refraction occurs due to the change in speed of light as it moves from one medium to another, causing it to bend towards or away from the normal depending on the speed change.
