Question

An electromagnetic wave of frequency v = 3.0 MHz passes from vacuum into a dielectric medium with relative permittivity ∈ = 4.0. Then

Answer 1

When an electromagnetic wave passes through a medium , then frequency remains unchanged.  The speed of electromagnetic wave inside a medium is given by,   v=(1/µe)0.5where,µ is permeability of the medium and e is permittivity of the medium.  In the above question the permeability is not given , hence if we consider the permeability of medium to be same as that of vacuum, then vspeed of electromagnetic wave falls by a factor of 2. As frequency remains unchanged,wavelength falls by a factor of 2.   speed=wavelength x frequency