(II) A cord has two sections with linear densities of 0.10 $\mathrm{kg} / \mathrm{m}$ and $0.20 \mathrm{kg} / \mathrm{m},$ Fig. $34 .$ An incident wave, given by $D=(0.050 \mathrm{m}) \sin (7.5 x-12.0 t),$ where $x$ is in meters and $t$ in seconds, travels along the lighter cord.
(a) What is the wavelength on the lighter section of the cord?
(b) What is the tension in the cord?
(c) What is the wavelength when the wave travels on the heavier section?