(a) State the difference between progressive waves and stationary waves in terms of the transfer of energy along the wave. (b) A progressive wave travels from left to right along a stretched string. Fig. 4.1 shows part of the string at one instant. . 4.1

(a) State the difference between progressive waves and stationary waves in terms of the transfer of energy along the wave. (b) A progressive wave travels from left to right along a stretched string. Fig. 4.1 shows part of the string at one instant. \nFig. 4.1 $P, Q$ and $R$ are three different points on the string. The distance between $P$ and $R$ is 0.48 m . The wave has a period of 0.020 s . (i) Use Fig. 4.1 to determine the wavelength of the wave. (ii) Calculate the speed of the wave.\nspeed = $\mathrm{ms}^{-1}$ (iii) Determine the phase difference between points $Q$ and $R$.\nphase difference = ${ }^{\circ}$