why wave does not have mass since it also consist of particles & particles do have mass??
If fact, most waves are made up of matter that does have mass. I suspect that you are referring to the principle exception to this, light! Light is made of oscillating electric and magnetic fields where the magnitudes of the electric and magnetic fields vary sinusoidally with time. Time varying electric fields give rise to magnetic fields while time varying magnet fields give rise to electric fields. In a sense light is a bit like a cat chasing its own tail! Some charged particle somewhere was forced to accelerate. As it did so it generated a time varying electric field. This time varying electric field then caused the generation of a time varying magnetic field which then generated a time varying magnetic field which then generated a time varying electric field, etc! Finally, somewhere in space this light wave then encounters a charged particle which it then causes to accelerate! So ultimately ALL light is caused by accelerating charged particles and ALL light ends its existence by accelerating a charged particle.