Ray Optics and Optical Instruments

Total Internal Reflection

  • Critical angle is the angle of incidence in denser for which angle of refraction in rarer medium is 90°
  • \tt \mu = \frac{1}{\sin C}
  • \tt \sin C = \frac{\mu_{rarer}}{\mu_{denser}} = \frac{V_{denser}}{V_{rarer}} = \frac{\lambda_{denser}}{\lambda_{rarer}}
  • CRed > CViolet (C = critical angle)
  • When angle of incidence in the denser medium is greater than critical angle light ray bounces back to the same medium and is called Total internal reflection
  • Field of vision of fish under water at depth h is r = h tan c = \tt \frac{h}{\sqrt{\mu^{2} - 1}} (r = radius of circle view)
  • Optical fibre works on the principle of T I R
  • Launching angle for optical fibre is \tt \sin i_{L} = \sqrt{\mu^{2}_{core} - \mu_{cladding}}
  • Optical fibres are used in communication and Laproscope, Cudoscope
  • Optical fibres are flexible, light weight, and non corrosive.

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Total internal reflection
\mu = \frac{1}{\sin C} = cosec \ C where μ → RarerμDenser