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3 marksRefraction

CSEC Physics · May/June 2007 · Paper 2 · Question 4(c)(iv)

An optical fibre is a flexible glass rod used to carry light signals. Figure 3 shows an optical fibre with a glass core (refractive index 1.50) surrounded by a cladding (refractive index n₂). Light ray AB in air is refracted into the core along path BC and then totally internally reflected.

Calculate the angle of incidence of the light entering the fibre.

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Other parts of this question

  1. 4(a)State what these theories considered light to be.[2 marks]
  2. 4(b)Indicate, by ticking the relevant boxes, the properties which these theories can explain. Place an X in the box if the theory CANNOT satisfactorily explain the…[4 marks]
  3. 4(c)(i)What is meant by 'total internal reflection' at point C?[2 marks]
  4. 4(c)(ii)Is the refractive index of the cladding greater or smaller than that of the core?[1 mark]
  5. 4(c)(iii)Draw on Figure 3, the ray that shows the path of the light continuing on from C.[1 mark]
  6. 4(c)(v)Given that the speed of light in air is 3 x 10⁸ m s⁻¹, determine the speed of light in the core of the fibre.[3 marks]

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