Problem Sheet 9

The numbers in square brackets refer to the number of the problem in your textbook.

  1. [E16.3] The absorption efficient of polyethylene for optical frequencies is 86.6 m-1. How thick a slab of polyethylene is required to reduce the transmitted light intensity to one-half of its initial value?
  2. [E16.5] It is proposed to replace soda glass windows of a greenhouse with polycarbonate (PC). Will the PC windows reflect more? The refractive index of the glass is 1.5 and that of PC 1.6.
  3. Can the refractive index of a material be negative? Why?
  4. Consider a material with negative refractive index. How does one interpret Snell's law for such a material. Explain with a figure.
  5. [E16.7] An X-ray system has a beryllium window to transmit the beam. The absorption coefficient of beryllium for the wavelength of X-rays of itnerest here is 3.02 x 102 m-1. If the window is 2 mm thick, what fraction of the incident beam intensity will pass through the window? The rest of the equipment is shielded with 4 mm of lead, with absorption coefficient for X-rays of 3.35 x 106 m-1. What fraction of the incident beam will escape through the casing?
  6. [E16.10] An optical fiber has a glass core with a refractive index of n1 = 1.48, clad with a glass with refractive index n2 = 1.45. What is the maximum angle that the incoming optical signal can deviate from the axis of the core while still remain trapped in it?
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