Refraction of Light

1. Refraction of Light Done by: Stephen Chow 3P304

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

3. Cherenkov Radiation

5. 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.

6. 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. 

7. 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.

8. 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. 

9. 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.

10. Binoculars

11. 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.

12. 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.

13. 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).

14. AIST Flat-Plate Lens

15. 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.

16. 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.

17. 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.

18. Princeton Novel Semiconductor Structure

19. 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.

20. 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.

21. 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.

22. Spectacles

23. 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.

24. 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

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

26. Thank you!