Light on air–plexi surface in this experiment mainly undergoes refraction (lower ray) and to a lesser extent reflection (top ray).

An image of the Golden Gate Bridge is refracted and bent by many differing three dimensional drops of water.

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 and momentum. 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 θ₂ is 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):

Failed to parse (Missing texvc executable; please see math/README to configure.): \frac{\sin\theta_1}{\sin\theta_2} = \frac{v_1}{v_2} = \frac{n_2}{n_1} .

In general, the incident wave is partially refracted and partially reflected; the details of this behavior are described by the Fresnel equations.

Explanation[link]

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.

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 slower in the more shallow 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 significance[link]

In 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 provides the sharpest, clearest vision.^[3]

Acoustics[link]

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. 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]

Gallery[link]

Refraction 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.

See also[link]

• Snell's law
• Huygens–Fresnel principle
• Birefringence (double refraction)
• Negative refraction
• List of indices of refraction
• Reflection
• Total internal reflection

References[link]

External links[link]

Wikimedia Commons has media related to: Refraction

• 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.
• Flash refraction simulation- includes source, Explains refraction and Snell's Law.
• Animations demonstrating optical refraction by QED

Bill Nye
Nye at Bridgewater State University in 2007
Born	(1955-11-27) November 27, 1955 (age 56)[1] Washington, D.C.[1]
Residence	Los Angeles
Fields	Mechanical engineering
Institutions	Boeing Cornell University Planetary Society
Alma mater	Cornell University (BS)
Known for	Bill Nye the Science Guy
Signature

William Sanford "Bill" Nye (born November 27, 1955),^[2] popularly known as Bill Nye the Science Guy, is an American science educator, comedian, television host, actor, mechanical engineer, and scientist. He is best known as the host of the Disney/PBS children's science show Bill Nye the Science Guy (1993–1998) and for his many subsequent appearances in popular media as a science educator.

Early life and career[link]

William Sanford Nye was born in Washington, D.C., the son of Jacqueline (née Jenkins; c. 1920–2000), a codebreaker during World War II, and Edwin Darby "Ned" Nye (died 1997), also a World War II veteran whose experience in a Japanese prisoner of war camp led him to become a sundial enthusiast.^[3][4][5] Nye is a fourth-generation Washington, D.C. resident on his father's side of the family. After attending Lafayette Elementary and Alice Deal Junior High in the city, he was accepted to the private Sidwell Friends School on a partial scholarship, graduating in 1973.^[6][7] He studied mechanical engineering at Cornell University, where one of his professors was Carl Sagan,^[8] and graduated with a Bachelor of Science in 1977.^[9] He was awarded an honorary doctorate by The Johns Hopkins University in May 2008. In May 2011, Nye was awarded an Honorary Doctor of Science degree from Willamette University where he was the keynote speaker for that year's commencement exercises.^[10]

Nye began his career in Seattle at Boeing, where, among other things, he starred in training films and developed a hydraulic pressure resonance suppressor still used in the 747. Later he worked as a consultant in the aeronautics industry. Nye told the St. Petersburg Times in 1999 that he applied to be a NASA astronaut every few years but was always rejected.^[11]

The Science Guy[link]

Nye began his professional entertainment career as an actor on a local sketch comedy television show in Seattle, Almost Live!; Nye attempted to correct the host of Almost Live! after the host pronounced "gigawatt" as "jigowatt."^[12][13] The character name came from the host's comment "Who do you think you are—Bill Nye the Science Guy?" and Nye was thereafter known as such on the program. His other main recurring role on Almost Live! was as Speedwalker, a speedwalking Seattle superhero.

Coincidentally, in 1991–93 he appeared in the live-action educational segments of Back to the Future: The Animated Series with a nonspeaking role as an assistant to Dr. Emmett Brown, played by Christopher Lloyd, in which he would demonstrate science with Lloyd's voice-over. The segments' national popularity led to Nye's hosting the educational television program Bill Nye the Science Guy from 1993 to 1998. Each of the 100 episodes aimed to teach a specific topic in science to a preteen audience, yet it garnered a wide adult audience as well. The show was very popular as a school resource and is still used to this day. He has written several books as The Science Guy. In addition to hosting the show, he was also a writer and producer for the series, which was filmed entirely in Seattle.

When portraying "the Science Guy", Nye wears a light blue lab coat and a bow tie and takes on the persona of an excited, jocular science educator. This popular image of Nye has been parodied by numerous sources, including the webcomic xkcd^[14] and the satirical news organization The Onion.^[15][16] In response to the fake headline "Crack Nearly Killed Me," Nye took the joke in good humor and sent The Onion an email thanking them for "dealing compassionately with this matter."^[17]

He appeared in his Science Guy persona alongside Ellen DeGeneres and Alex Trebek in Ellen's Energy Adventure, an attraction that has played since 1996 at the Universe of Energy pavilion inside Epcot at Walt Disney World. He also has a voice-over at the DINOSAUR attraction in Disney's Animal Kingdom park, where he tells guests about the dinosaurs while they queue for the ride. In addition, he appears in the "Design Lab" of CyberSpace Mountain inside DisneyQuest at Walt Disney World, where he refers to himself as "Bill Nye the Coaster Guy."

[edit] Post-Science Guy career

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Bill Nye "The Science Guy" and Executive Director of The Planetary Society received the Committee for Skeptical Inquiry's "In Praise of Reason" Award at CSICON 2011 in New Orleans

Nye remained interested in science education through entertainment. He created a 13-episode PBS KCTS-TV series about science, called The Eyes of Nye, aimed at an older audience than his previous show had been. Airing in 2005, it often featured episodes based on politically relevant themes such as genetically modified food, global warming, and race.

He played a science teacher in Disney's 1998 TV movie The Principal Takes a Holiday; he made a hovercraft in order to demonstrate science in an unusual classroom manner. From 2000 to 2002, Nye was the technical expert in BattleBots. In 2004 and 2005, Nye hosted 100 Greatest Discoveries, an award-winning series produced by THINKFilm for The Science Channel and in high definition on the Discovery HD Theater. He was also host of an eight-part Discovery Channel series called Greatest Inventions with Bill Nye.

Nye has guest-starred in several episodes of the crime drama Numb3rs as an engineering faculty member. A lecture Nye gave several years ago on exciting children about math was an inspiration for creating the Numb3rs show.^[18]

Bill joined the American Optometric Association in a multimedia advertising campaign to educate parents on the importance of getting their children a comprehensive eye examination.^[19]

He was a regular in TV Land discussions. He has also made guest appearances on the VH1 reality show America's Most Smartest Model.^[20]

Nye appears in segments of The Climate Code on The Weather Channel, telling his personal ways of saving energy. He still makes regular appearances on the show, often asking quiz questions.

As of fall 2008, Nye also appears on the daytime game show Who Wants to Be a Millionaire as part of the show's reintroduced "Ask the Expert" lifeline. In 2008, he also hosted Stuff Happens, a show on the then new Planet Green network.

In November 2008, Nye appeared in an acting role as himself in the fifth-season episode "Brain Storm" of Stargate Atlantis alongside fellow television personality and astrophysicist Neil deGrasse Tyson.^[21]

Nye has appeared numerous times on the talk show Larry King Live, speaking about topics such as global warming^[22] and UFOs.^[23] He argued that global warming is an issue that should be addressed by governments of the world in part because it could be implicated in the record-setting 2005 Atlantic hurricane season. On UFOs he has been skeptical of extraterrestrial explanations for sightings such as those at Roswell and Malmstrom Air Force Base in 1967.

In 2009, portions of Bill Nye's shows were used as lyrics and portions of the second Symphony of Science science education music video by composer John Boswell.

Nye recorded a short YouTube video (as himself, not his TV persona) advocating clean energy climate change legislation on behalf of Al Gore's Repower America campaign in October 2009.^[24]

Nye (as his TV persona) also made a guest appearance on The Dr. Oz Show.

On March 12, 2011, Nye made an appearance on CNN to discuss the evolving nuclear incidents in Japan as a result of the devastating earthquake and tsunami there. Nye erroneously stated that cesium is used to "slow and control" the nuclear reaction. ^[25] In reality, cesium (specifically cesium-137) is a nuclear fission product, not a control rod material. Nye also erroneously stated that the nuclear reactor involved in the Three Mile Island incident is still running and that the use of boron to slow the nuclear chain reaction is uncommon, when in fact boron-10 is commonly used in control rods, and is circulated in the coolant of reactors in the United States, as well as stored on site as a method of emergency shutdown.^[26][27]

A solar noon clock atop Rhodes Hall was gifted from Nye to Cornell on Aug. 27 following a public lecture that filled the 715-seat Statler Auditorium. Nye talked about his father's passion for sundials and timekeeping, his time at Cornell, his work on the sundials mounted on the Mars rovers and the story behind the Bill Nye Solar Noon Clock. ^[28]

Life outside television[link]

Nye speaking in 2010.

In the early 2000s, Nye assisted in the development of a small sundial that was included in the Mars Exploration Rover missions. Known as MarsDial, it included small colored panels to provide a basis for color calibration in addition to helping keep track of time.^[29] From 2005 to 2010 Nye was the vice president of The Planetary Society, an organization that advocates space science research and the exploration of other planets, particularly Mars.^[30] He became the organization's second Executive Director in September 2010 when Louis Friedman stepped down.^[31][32]

In November 2010, Nye became the face of a new permanent exhibition at the Chabot Space & Science Center in Oakland, CA. Bill Nye’s Climate Lab features Nye as commander of the Clean Energy Space Station, and invites visitors on an urgent mission to thwart climate change. Beginning with a view of Planet Earth from space, visitors explore air, water, and land galleries to discover how climate change affects Earth’s connected systems, and how to use the Sun, wind, land, and water to generate clean energy. In an interview about the exhibit, Nye said, “Everything in the exhibit is geared to showing you that the size of the problem of climate change is big. Showing you a lot about energy use... It’s a huge opportunity... We need young people, entrepreneurs, young inventors, young innovators to change the world.” ^[33]

He holds several United States patents,^[34] including one for ballet pointe shoes^[30] and another for an educational magnifying glass created by filling a clear plastic bag with water.^[35][36] From 2001–2006 Nye served as Frank H.T. Rhodes Class of '56 University Professor at Cornell University.^[9][37] Nye supported the 2006 reclassification of Pluto from a planet to a dwarf planet by the International Astronomical Union.^[38]

Since 2006, Nye has lived in Los Angeles in a house with modifications, though has owned a house on Mercer Island.^{[citation needed]} As of July 2007, Nye and environmental activist Ed Begley, Jr. are engaging in a friendly competition "to see who could have the lowest carbon footprint," according to Begley.^[39] In a 2008 interview, Nye joked that he wants to "crush Ed Begley" in their environmental competition.^[40] Nye and Begley are neighbors in Los Angeles, and sometimes dine together at a local vegetarian restaurant.^[40] Nye often appears on Begley's Planet Green reality show Living with Ed.

Nye made an appearance in Palmdale's 2010 video "Here Comes the Summer"^[41]; the band's lead singer Kay Hanley is his neighbor.

Nye is a fellow of the Committee for Skeptical Inquiry, a U.S. non-profit scientific and educational organization whose aim is to promote scientific inquiry, critical investigation, and the use of reason in examining controversial and extraordinary claims.^[42]

Interviewed by John Rael for the Independent Investigation Group IIG, Nye stated that his "concern right now... scientific illiteracy... you don't [the public] have enough rudimentary knowledge of the universe to evaluate claims."^[43]

Personal life[link]

Nye announced his engagement during an appearance on The Late Late Show with Craig Ferguson and was married briefly to his fiancée of five months, author Blair Tindall, on February 3, 2006. The ceremony was performed by Rick Warren at The Entertainment Gathering at the Skirball Cultural Center in Los Angeles. Yo-Yo Ma provided the music.^[44] Nye left the relationship seven weeks later when the marriage license was declared invalid;^[45] their impromptu ceremony, which preceded the license purchase, violated California state law, said Tindall in a radio interview.^[46] Nye later secured a temporary restraining order against Tindall after she entered his property late at night to pour weed killer in his garden.^[45]

Nye enjoys baseball and occasionally does experiments involving the physics of the game. As a longtime Seattle resident before becoming an entertainer, he is said to have been a fan of the Seattle Mariners, although recently he has voiced his preference (as a D.C. native) for the Washington Nationals.^[6]

References[link]

External links[link]

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Biography portal

Wikimedia Commons has media related to: Bill Nye

• Official website
• Bill Nye at the Internet Movie Database
• Bill Nye on Twitter
• Nye-Tindall wedding video
• An interview/discussion with Nye as guest on the radio show Loveline
• "Changing The World With Science Education" interview on Point of Inquiry.
• Seattle Times interview (April 26, 2004)
• Science Channel interview