Question

1. Which of the following is a better theory? Explain your choice.
   1. Law of reflection assuming light as particles;
   2. Law of refraction assuming light as particles;
   3. Fermat’s principle.

Answer 1

Solution

c. Fermats Principle.

As we know light is not just particle or just a wave. It shows the dual nature. Sometimes we require it's wave nature to describe certain phenomenon like diffraction, interference etc. Whereas in sitations like photoelectric effect we require it's particle nature. So any theory which does not rely on either particle or wave nature of light appears more elegant, like the Fermat's principle. Fermat's principle just says that light always take the optimum path that takes minimum time to traverse. We can explain many of light phenomenon using Fermat's principle. Also Fermat's principle is in close resemblance with least action principle of classical mechanics, which says the action integral is always minimum for correct path of system. Thus due to these reasons Fermat's principle is more elegant than the other two.