thank you for taking your valuble time to answer.

i have one more question,( i am new to this field of study sorry for asking very fundamental question)

i am doing the experiment on exciting plasmon with kretschmann method.

using a 40nm gold film deposited on a slide glass.as for now im trying out water as the index matching layer between the prism and the slide gass which contains the layer.

my question is how do i calculate the plasmon excitaiton angle(with numerical calculation)  for this specific setup ?

thank you