Two progressive waves on the same string are described by y1(x,t)=Asin(6πx−120πt+ϕ) and y2(x,t)=Asin(6πx+120πt+ϕ), with the usual SI units. Answer the following.
(i) For each wave, write expressions for its wavelength and frequency in terms of the given numerical coefficients.
(ii) Explain which wave propagates towards the positive x-axis and which towards the negative x-axis.
(iii) Show that the speeds of the two waves are equal even though they travel in opposite directions.