length in time of 1 period at a given frequency


500Hz -  2.00ms
200Hz -  5.00ms
100Hz - 10.00ms
 80Hz - 12.50ms
 70Hz - 14.29ms
 60Hz - 16.67ms 
 50Hz - 20.00ms
 40Hz - 25.00ms
 30Hz - 33.33ms
 20Hz - 50.00ms