If you see an ocean wave hit the beach every 8 seconds what is its frequency (in Hz)
0.125
0.250
0.800
8.0
16.0
The frequency is the number of wave cycles per second, so it is equal to 1 divided by the time period of one wave cycle.
The time period of one wave cycle is 8 seconds.
Therefore, the frequency is 1/8 = 0.125 Hz.