1.why can a sound wave not be polarised?2.a pure sine wave has a unique frequency but a disturbance of other waveform may have many frequency components in it ,elplain with example like clapping of our hand.3.why is wavefront normal to direction of propogation of sound wave for a homogenous and isotropic medium?4.is speed of sound wave equal to speed of particles of medium?5.why is description of sound wave more appropriate in terms of pressure wave than in terms of displacement wave?

Ans 1--Sound in air can only be a longitudinal wave, not a transverse wave hence it cannot be polarized
2-pure sine wave has a unique frequency ,as a n example if we take any wave shape and filter out all frequencies, except the lower frequency , the result will be a pure sine wave at that frequency. now if we clap our hands together.the vibration transfers energy to nearby air particle which produces sound wave in air
3- wave front in sound wave is normal to direction of propagation because the medium is isotropic which means the particles are spread homogeneously an hence the energy imparted by sound waves is equally distributed and hence wave front is normal to direction of propagation.
4- No the particle of medium moves with particle velocity and sound wave itself moves with sound speed which is 343m/s
5- sound wave is a pressure wave means a mechanical wave which results from back and forth vibrations of the particle of the medium through which sound travels hence we describe it in terms of pressure wave.