3. Waves in a puddle are made by plunging a stick in and out of the water every four seconds. What is the frequency of the waves?

c.

The PERIOD of oscillations is 4 seconds. Check out the units! Since we have units of seconds they may as well be related to period, not frequency!

We than use:

f=1/P

or

f=1/4sec

which is

f=0.25 1/sec

or 0.25 Hz (same thing!)

Note: This is one out of two questions (The other being 5) in which some math was required.