When is the amplitude coefficient of reflection parallel to the incidence plane zero?

[alchemist7]

At what angle of incidence is amplitude coefficient of reflection parallel to the incidence plane 0?

my solution is that by Fresnell's equation, r//=tan(i-i`)/tan(i+i`)=0, i=i`,i=90.so for whatever surface,angle of incidence should be 90.

is it correct? different from the answer!

 

[LowlyPion]

Is what you're trying to find the Brewster's angle by any chance?

http://en.wikipedia.org/wiki/Brewster's_angle