**Problem : **
As light moves from air (*n* 1.00) to amber it deviates 18^{o} from its 45^{o} angle of
incidence. Which way does it bend? What is the speed of light in amber?

**Problem : **
A transparent fiber of index of refraction 1.6 is surrounded (cladded) by a less dense plastic of index
1.5. At what angle must a light ray in the fiber approach the interface so as to remain within the fiber?

**Problem : **
A light ray in air approaches a water surface (*n* 1.33) such that its electric vector is parallel to the
plane of incidence. If *θ*_{i} = 53.06^{o}, what is the relative amplitude of the reflected beam? What
about if the electric field is perpendicular to the plane of incidence?

r_{ || } = 0 |

In the latter (perpendicular) case we have

r_{âä¥} = = - 0.278 |

In the former case, no light is reflected -- this is called Brewster's angle as we shall see in the section on polarization. For the perpendicular field the amplitude of the reflected wave is 0.278 as large as the incident wave. That is the reflected ray is about (0.278)

**Problem : **
By what angle do blue light (*λ*_{b} = 460 nm) and red light (*λ*_{r} = 680 nm) disperse upon entering
(from vacuum) a medium with *N* = 7×10^{38}, *ε* = 1.94, and *σ*_{0} = 5.4×10^{15} Hz at
an incident angle of 20^{o} (the electron charge is 1.6×10^{-19} Coulombs and its mass is 9.11×10^{-31} kilograms)?

n_{r}^{2} = 1 + = 1 + = 1 + 0.472 |

Thus

n_{b}^{2} = 1 + = 1 + = 1 + 0.821 |

Thus

**Problem : **
What is the rate of change of the speed of light with angular frequency in a dielectric medium?

= | |||

âá’1n = |

Now we must take the derivative of this with respect to

= |

The required derivative is just

= |

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