in fact, the experts in microwave engineer already know it but since i am not an microwave expert, I liked something I learned today. skin depth gives a measure of the depth to which electromagnetic radiation can penetrate a conducting surface. for good conductors, the amplitude of the fields in the conductor decay by an amount of 1/e after the skin depth of this conductor. For microwave frequencies, the skin depth of most conductors is very small. Thanks to this property, we can have low-loss microwave components with thin plating. If we had higher skin depth, we would use thicker conductors to have less loss.
for example, Consider electromagnetic wave of frequency 1 MHz for copper (Cu). By using proper values, one gets the skin depth in Cu to be about 0.067 mm. thus using copper plates thinner than 1/10 of 1 mm will be sufficient to have low loss.
