Refraction of Light

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Refraction of Light

• Done by Stephen Chow 3P304

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Agenda

• 5 technologies of Refraction Of Light
• Cherenkov Radiation
• Binoculars
• AIST innovations Flat-Plate Lens
• Princeton Novel Semiconductor Structure
• Spectacles

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Cherenkov Radiation
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(No Transcript)
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Cherenkov Radiation

• Cherenkov Radiation is an electromagnetic
  radiation emitted when a charged particle (such
  as an electron) passes through an insulator at a
  constant speed greater than the speed of light in
  that medium. The characteristic blue glow of
  nuclear reactors is due to Cherenkov radiation.
• It is named after Russian scientist Pavel
  Alekseyevich Cherenkov, the 1958 Nobel Prize
  winner who was the first to characterise it
  rigorously.

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Cherenkov RadiationIntroduction

• Is there an equivalent of the
• sonic boom for light?
• A sonic boom is a shock wave which propagates
  from an aircraft or other object which is going
  faster than sound through the air (or other
  medium). 
• In subsonic flight air is deflected smoothly
  around the wings.  In supersonic flight this
  cannot happen because the effect of the aircraft
  wings pushing the air ahead cannot travel faster
  than sound. 

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Cherenkov RadiationIntroduction

• The result is a sudden pressure change or shock
  wave which propagates away from the aircraft in a
  cone at the speed of sound.
• It is thought that objects cannot travel faster
  than c, the speed of light in vacuum. Furthermore
  there is no ether to act as a medium being pushed
  aside like the air is pushed by an aircraft. 
• Therefore no light equivalent of the sonic boom
  can occur in vacuum.

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Cherenkov Radiation

• In a medium such as water, the speed of light is
  considerably less than the speed of light in
  vacuum.
• In a medium with refractive index n the velocity
  of light is vlight c/n.  The refractive index
  is always greater than one so it is possible for
  a particle to travel through water (nwater 1.3)
  or other media at a speed faster than the speed
  of light in that media. 
• When a charged particle does so, a faint
  radiation is produced from the medium. 
• The charged particle excites the water molecules
  which then return to their normal state emitting
  photons of blue light. 

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Cherenkov RadiationUses

• Cherenkov radiation is widely used to facilitate
  the detection of small amounts and low
  concentrations of biomolecules.
• Cherenkov radiation is used to detect high-energy
  charged particles.

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Binoculars
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Binoculars

• To see something in the distance, you can use two
  convex lenses, placed one in front of the other.
  The first lens catches light rays from the
  distant object and makes a focused image a short
  distance behind the lens.
• This lens is called the objective, because it's
  nearest to the object you're looking at. The
  second lens picks up that image and magnifies it.

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Binoculars

• Binoculars are simply two telescopes side by
  side, one for each eye. However, when light rays
  from a distant object pass through a convex lens,
  they cross over.
• That's why distant things sometimes look upside
  down if you look at them through a magnifying
  glass. Hence, binoculars have a pair of prisms
  inside them to rotate the image through 180
  degrees.

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Binoculars

• One prism rotates the image through 90 degrees,
  then the next prism rotates it through another 90
  degrees, so the two prisms effectively turn it
  upside down. The prisms can either be arranged in
  a back-to-back arrangement (known as roof prisms)
  or at 90 degrees (known as Porro prisms).

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AIST Flat-Plate Lens
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AIST Flat-Plat Lens

• Experiments with holograms have led to a
  thin-film flat-plate lens that has a periodic
  (layered) structure and that is capable of a
  resolution of 100nm or finer.
• No other current lens system can do this.
• Because of its layered, thin-film construction,
  the flat lens provides excellent image-forming
  characteristics by the incidence oflight having
  a wavelength slightly shorter than the
  wavelength corresponding to the frequency
  period of the thin film.

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AIST Flat-Plate Lens

• The periodic, thin-film structure can exhibit a
  negative refractive index at high angles of
  incidence.
• Detailed studies have been performed on the
  relationship between the periodic structure and
  the wavelength, distance between the light source
  and the flat-plate lens, and the image-formation
  characteristics of the overall optical system.

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AIST Flat-Plate Lens

• Applications include high-density optical digital
  data recording and retrieval, and other
  applications demanding fine resolution or
  negative refractive index.
• It is discovered that, at high angles of
  incidence, the AIST flat-plate lens can achieve a
  negative refractive index, thus in theory
  allowing imaging smaller than that of the
  wavelength of light it is using.

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Princeton Novel Semiconductor Structure
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Princeton Novel Semiconductor Structure

• While developing new lenses for next-generation
  sensors, researchers have crafted a layered
  material that causes light to refract, or bend,
  in a manner nature never intended.
• Refraction always bends light one way, as one can
  see in the illusion of a "bent" drinking straw
  when observed through the side of a glass.
• A new metamaterial crafted from alternating
  layers of semiconductors (indium-gallium-arsenic
  and aluminum-indium-arsenic) acts as a single
  lens that refracts light in the opposite
  direction.

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Princeton Novel Semiconductor Structure

• With the new metamaterial, flat lenses are
  possible, theoretically allowing microscopes to
  capture images of objects as small as a strand of
  DNA.
• The current metamaterial lens works with infrared
  light, but the researchers hope the technology
  will expand to other wavelengths in the future.

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Princeton Novel Semiconductor Structure

• This startling property may contribute to
  significant advances in many areas, including
  high-speed communications, medical diagnostics
  and detection of terrorist threats.

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Spectacles
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Spectacles

• Corrective lenses are used to correct refractive
  errors of the eye by modifying the effective
  focal length of the lens in order to alleviate
  the effects of conditions such as nearsightedness
  (myopia), farsightedness (hyperopia) or
  astigmatism.

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Spectacles

• When light shines into the lens, the lens refract
  the light rays inward to meet at the back of the
  eye, where the image is recorded, so that the
  image would be clear and sharp.
• If the light rays do not converge at the back of
  the eye, a blurred image would be seen

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Acknowledgements

• www.google.com.sg
• www.yet2.com
• www.projectrho.com
• www.princeton.edu.com

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Thank you!