Magnetic field lines permeability in vacuum We know that permeability is the property of the medium to permit the magnetic fields but vacuum is not a physical thing as i know till now then how it allows magnetic fields to pass through it...I mean how much it permits magnetic field through it
 A: Permittivity just means how easily the electric field can exert influence over the space. The higher the the permittivity the harder is for electric field to exert force on a charge at fixed difference away.
A vacuum has the lowest permittivity which means that electric field function best in vacuum. Material having higher permittivity is due to their dielectric constants so it is harder for electric field to exert influence in these materials.  Same is the case with magnetic fields.
A: I think the problem you're having is that you're thinking of the field as a thing that travels through space, when it's nothing of the sort. The field is a property that exists everywhere, always. That field then takes particular values that may or may not be zero at any given time.
Now, when we talk about the permeability or permittivity of vacuum we're making a linguistic extrapolation that doesn't actually make sense, as you've noticed. If you have some material objected you can describe it's effects on electromagnetic fields as being the ability of the effects on the field to permeate through the object compared to when the object is not there, but asking about permeability in the absence of space doesn't even make sense. Empty space is the reference for which we define permeability or permittivity.
Thus, the permeability or permittivity of free space are misnomers: they're unit conversion factors left over from the history of how electromagnetic fields and charges were originally defined, and how units were attached to them, not physically interesting quantities. You can think of them as being akin to 0 degrees Celsius or Fahrenheit, or 1 atmosphere of pressure: something that was set at a convenient value based on circumstances.
That said, you can derive two physically interesting quantities from them: the speed of light in a vacuum $c = 1/\sqrt{\mu_0\epsilon_0} \approx 3\times10^8\,\mathrm{m/s}$ and the impedance of free space $Z_0 = \sqrt{\mu_0 / \epsilon_0}\approx 377\,\Omega$. The latter is a useful quantity to think about when you start dealing with waves, particularly with wave guides and transmission lines.
