Question

what is the amplitude of the wave? 9 cm 27 cm 18 cm 2 cm

Explanation:

Step1: Recall Amplitude Definition

Amplitude is the maximum displacement from the equilibrium (midline) to a peak (or trough) of a wave. From the graph, the total vertical distance from peak to trough is related to amplitude. If the vertical range (peak to trough) is, say, 18 cm (from the options, 18 cm is a total range), then amplitude is half of that.

Step2: Calculate Amplitude

If the distance from peak to trough is 18 cm, amplitude $A=\frac{18}{2}=9$ cm. So the amplitude is 9 cm.

Answer:

9 cm (corresponding to the option with "9 cm")