Q.E.D.

[bwanaaa]

In optics i learned that the angle of reflection=angle of incidence.

But Feyneman argued that was an illusion.

Is this what he said?
light is scatterred in all direcctions from all points of a surface equally-it's just that the interference cancels out all light that isnt located where the angle of reflection=angle of incidence.

 

[RossGr]

Its been a while since I read the book, I don't recall Feynman calling it an illusion.

Yes, you are essentially correct.

 

[bwanaaa]

If that hypothesis is correct, then I am troubled by the following fact-

the energy and intensity of the reflected beam is very close to that of the incident beam. If light is truly being scattered through 180 degrees and the reflected beam is the only one not canceled out by interference, shouldnt its energy be much, much less than the incident beam?

 

[rjain]

It's merely an approximation, not an illuision. In the same way that the laws of thermodynamics are an approximation. The laws of thermodynamics are basically a result of the law of averages.

Light "rays" don't travel in a straight line. That's why you have this interference. If the energy reflected were much less than the energy incident, then that energy would have to go somewhere. The energy doesn't interfere with itself, it's the EM fields that interfere. The end result is a conservation of the energy. The energy that is not reflected is absorbed into the reflecting medium as heat or is transmitted (refracted).