Non optical telescopes presentation

6.913 visualizações

Publicada em

Publicada em: Educação, Tecnologia, Negócios
  • Seja o primeiro a comentar

  • Seja a primeira pessoa a gostar disto

Non optical telescopes presentation

  1. 1. Radio TelescopesInfrared and UV TelescopesX- Ray telescopesTwo EquationsThe Rayleigh Criterion for resolving power
  2. 2. Radio Waves have a much Longer WavelengthThan Light.Therefore for a radio telescope to have the sameResolving power as an optical telescope, dishNeeds to be very large. (see Rayleigh Criterion,Last slide)Resolving power of a single radio telescope isWorse than the eye therefore many needs to becombinedAn antenna is used as a detector at the focalPoint. There is no equivalent to the eye lens as inOptical telescopes.Most are manoeuvrable allowing source to beTracked. Telescope moves with the source as EarthRotates.
  3. 3. IR and UV telescopes both use parabolic mirrors to focus radiation onto a detector as inOptical reflecting telescopesThe atmosphere of the Earth absorbs most of the wavelengths of lightTherefore Infrared and UV telescopes needs to be launched into the space and setIn orbit.Light and Radio waves can pass the atmosphere but not infrared and UVBoth types use CCDs or special photographic paper as radiation detectors as in opticalTelescopes.Longer the wavelength of radiation, less they are affected by imperfections in mirrors.So IR telescopes don’t need to be perfectly shaped as in optical telescopes.IR telescopes have a problem in that they produce their own infrared radiation becauseOf their temperature. This is overcome by cooling them to very low temperature usingLiquid helium or refrigeration units. IR and UV telescopes both use parabolic mirrors to focus radiation onto a detector as in Optical reflecting telescopes Both types use CCDs or special photographic paper as radiation detectors as in optical Telescopes. Longer the wavelength of radiation, less they are affected by imperfections in mirrors. So IR telescopes don’t need to be perfectly shaped as in optical telescopes.
  4. 4. X-rays reflect if they just graze a mirrors surface. By using a series of nested mirrors, weCan gradually change the direction just enough to bring them to a focus on a detector.This type of telescope is called a grazing telescope.X-rays don’t reflect off surfaces in same way as most other Electromagnetic radiationUsually x-rays are either absorbed by a material or it passes straight through it X-rays can be detected using a modified Geiger counter or a fine wire mesh. X-rays don’t reflect off surfaces in same way as most other Electromagnetic radiation Usually x-rays are either absorbed by a material or it passes straight through it X-rays reflect if they just graze a mirrors surface. By using a series of nested mirrors, we Can gradually change the direction just enough to bring them to a focus on a detector. This type of telescope is called a grazing telescope.
  5. 5. In general X-rays have a much smaller collecting power than other types of telescopesRayleigh criterionMinimum angle that can be resolved ≈ Wavelength (λ) (Ѳ) Diameter of objective lens (D)A UV telescope has a much better resolving power than a radio telescope for the sameSize of dish.The Collecting power is Proportional to the area:Power ∝ Diameter2For a radio, optical, UV or IR telescope, this is the area of the objective mirror or dish
  6. 6. This is an equation to work out the resolution of a telescope Two stars Telescope 1 The angle, θ, which the telescope can resolveThe angle, θ, which the telescope can resolve Two stars Telescope 2The equation θ (minimum angle that can be resolved ) = λ (wavelength of radiation) D (Diameter of aperture )If two stars are very close together, it can be difficult to see them using a telescope, as they appearCould appear blurred.For a telescope, D is the diameter of objective lens or objective mirror. Both λ and D are in metres.Θ in radians. The smaller the value of θ, the better the resolving power (telescope 2 above has aHigher resolution than telescope 1, because the angle which telescope 2 can resolve is smaller)!.Therefore, increasing the value of D, gives you a better resolution, as θ gets smaller.

×