Due to the attractive and repelling electric forces in the matter, the group of positively and negatively charged particles act in a joint manner is called as plasma. The number which says about the propagation of light through the medium is called as refractive index. Here is the online plasma refractive index calculator that calculates based on the inputs of plasma frequency and frequency.
Calculate the plasma refractive index with the plasma frequency of 20 and frequency of 100.
Plasma refractive index = [ 1 - ( 20 / 1002 ) ] 1 / 2