A wave is moving along a string. The equation giving the displacement y of a point at coordinate x and at time t has the form y = 0.2cos(4pi(x)/5-20pi(t)), where the units are in meters and seconds.
i.) Calculate the frequency and the speed(m/s) of the wave.
ii.) By reflecting this wave from a rigid support, standing transverse waves are set up on a stretched string. It is observed that the string is vibrating in its SECOND HARMONIC. Calculate the length of this string in meters.