c = f*L
If you cant remember this just consider the units of each (denoted [c] is units of c):
[c] = meters/second, [f] = 1/seconds or Hertz, [L] = meters
So [c] = [f*L], an easy way to remember it.
So to get the frequency, just solve for f:
f = c/L = (3.00 x 10^8)/(5.93 x 10^-7) m/s = 5.05902192 × 10^14 m/s ~ 5.06 x 10^14 m/s
