Answer the following questions related to mechanical waves in a medium:
a. (i) Define a progressive (travelling) wave.
b. (ii) State the fundamental difference between a transverse wave and a longitudinal wave with respect to the direction of particle vibration.
c. (iii) What is meant by the statement "There is no net transport of matter in a mechanical wave"? Explain in one or two sentences.
d. (iv) List two everyday observations that support the idea you have stated in part (iii).