- A wave has the equation (x in metres and t in seconds) Y = 0.02sin(30t – 4x). Find i. Its frequency, speed and wave length. ii. The equation of wave with double amplitude but travelling in the opposite direction. Ans: 4.77 Hz, 1.57 m, 7.5 ms^-1, y = 0.04sin(30t + 4x)