Two dippers $D_1$ and $D_2$ are joined to a motor and a d.c. power supply. At first, only $D_1$ oscillates at the water surface to create waves. Fig. 7.2 shows how the displacement $y$ of the water varies with distance $x$ from $D_1$ at one instant. Using Fig. 7.2, determine the amplitude of the wave.
Determine the wavelength of the wave from Fig. 7.2.
Both dippers $D_1$ and $D_2$ are set vibrating, so waves are generated by each dipper on the water surface. State and explain whether these waves are stationary or progressive.
Explain why $D_1$ and $D_2$ are linked to the same motor.
In Fig. 7.3, the distances of $A$ and $B$ from $D_1$ and $D_2$ are shown. State and explain how the water surface displacement at $A$ varies with time.
State and explain how the surface displacement of the water at $B$ varies with time.