Transcript Refraction of Light

Refraction of Light
Done by: Stephen Chow 3P304
Agenda
• 5 technologies of Refraction Of Light
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Cherenkov Radiation
Binoculars
AIST innovations: Flat-Plate Lens
Princeton Novel Semiconductor Structure
Spectacles
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.
Cherenkov Radiation
Introduction
• 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.
Cherenkov Radiation
Introduction
• 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.
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.
Cherenkov Radiation
Uses
• 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.
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.
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.
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).
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 of
light having a wavelength slightly
shorter than the wavelength
corresponding to the frequency
period of the thin film.
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.
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.
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 aluminumindium-arsenic) acts as a single lens that refracts light in
the opposite direction.
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.
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.
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.
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
Acknowledgements
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www.google.com.sg
www.yet2.com
www.projectrho.com
www.princeton.edu.com
Thank you!