If a wave were nine feet high, how much would the amplitude be? a. 3 feet b. 4.5 feet c. 12 feet d. 18 feet

B. 4.5 feet

Explanation:

The amplitude of a wave corresponds to the maximum displacement of a wave from its equilibrium point.

In this problem, the text tells us the total height of the wave, which corresponds to the distance measured from the maximum of the wave to its minimum. However, the equilibrium point corresponds to the point where the amplitude of the wave is zero: therefore, the equilibrium point lies half-way between the maximum and minimum.

As a consequence, the amplitude of the wave is half the height of the wave, therefore:

So, the correct answer is

B. 4.5 feet

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