State what is meant by the wavelength of a progressive wave.

1. (a)State what is meant by the wavelength of a progressive wave.[1]
2. (b)A cathode-ray oscilloscope (CRO) is used to analyse a sound wave. The screen of the CRO is shown in Fig. 5.1. [Figure 5.1] The time-base setting of the CRO is 2.5mscm⁻¹. Determine the frequency of the sound wave. frequency =[2]
3. (c)The source emitting the sound in (b) is at point A. Waves travel from the source to point C along two different paths, AC and ABC, as shown in Fig. 5.2. [Figure 5.2] Distance AB is 8.0m and distance AC is 20.8 m. Angle ABC is 90°. Assume that there is no phase change of the sound wave due to the reflection at point B. The wavelength of the waves is 1.6m.
4. (c)(i)Show that the waves meeting at C have a path difference of 6.4m.[1]
5. (c)(ii)Explain why an intensity maximum is detected at point C.[2]
6. (c)(iii)Determine the difference between the times taken for the sound to travel from the source to point C along the two different paths. time difference =[2]
7. (c)(iv)The wavelength of the sound is gradually increased. Calculate the wavelength of the sound when an intensity maximum is next detected at point C. wavelength =[1]

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