WAEC Physics 2018 Paper

Concept:The number of wavelengths in a wave pattern is equal to the number of complete oscillations or cycles shown in the diagram.Explanation:From the diagram, count the fractions of a wavelength section by section.The wave consists of $\frac{1}{4}$ wavelength at the beginning, followed by four parts of $\frac{1}{2}$ wavelength each, and then $\frac{1}{4}$ wavelength at the end.Total number of wavelengths:$$\frac{1}{4} + \frac{1}{2} + \frac{1}{2} + \frac{1}{2} + \frac{1}{2} + \frac{1}{4} = 2\frac{1}{2}$$Therefore, the waveform contains $2\frac{1}{2}$ wavelengths.Answer:C. $2\frac{1}{2}$