IB Physics Critical Angle

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A tutorial sheet on critical angle, a topic in SL waves, is given below.

  1. Define the term critical angle.
  2. Why can total internal reflection only occur if the wave speed in the first region is less than the wave speed in the second region?

  3. A diver is at a depth of 3.0 m in water of refractive index 1.3. The diver looks upwards. What is the diameter of the image of the horizon that they see?

  4. An electromagnetic wave strikes the end of an optical fibre at an angle 𝜽 to the normal. The refractive index of the cladding layer is n 2 and the refractive index of the optical fibre is n 1 . Show that the maximum value of 𝜽 which allows transmission of light along the fibre is given by sin𝜽 = (n1 2 -n2 2 ) 1/2 .

  5. For more applications of critical angle see Physics Education Vol 17, No 2, March 1982, p 86