Which of the following statements about mechanical waves is TRUE?
O When two strings of different densities are tied together, a wave disturbance must be transmitted through the two strings with the sum amplitude
O The velocity of a propagating wave on a string decrease as tension on the string increases
O When a mechanical wave encounters a fixed boundary, the reflected wave is inverted
O When a string of length is fixed on both sides and allowed to resonate, the first two harmonic wavelengths are 2l and l/2
O In a transverse mechanical wave, each particle on the wave moves parallel to the direction of the propagating wave disturbance