physics- Light key points

12/18/2011 CBSE

  • If two plane mirrors are inclined to each other at 900 the emergent ray is
    anti-parallel to incident ray, if it suffers one reflection from each.
    Whatever be the angle of incidence.
  • In concave mirror, minimum distance between a real object and its real
    image is zero. (i.e. when u = v = 2 f).
  • In the refraction intensity of incident light decreases as it goes from
    one medium to another medium.
  • The refractive index of a transparent medium is the ratio of the speed of
    light in vacuum to that in the medium.
  • During refraction wavelength vanes but frequency remains unchanged.
  • The size of the object perceived by the eye is proportional to the visual
    angle subtended by the object or image at the eye.
  • When we look distant objects, the eye is relaxed and its focal length is
    largest.
  • In presbyopia, the corrective lens is bifocal lens.
  • In astigmation, the corrective lens is cylindrical lens with proper axis.
  • Scattering of light is due to the blue colour of sky and the reddening of
    the sun at sunrise and sunset.
  • The energy available due to the difference in the temperature of water at
    the surface of the ocean and at deeper levels is called Ocean Thermal Energy (OTE)
  • Fossil fuels are the energy rich compounds of carbon which were originally
    made by plants with the help of sun's energy (by photosynthesis) when these
    plants were alive millions of years ago.

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