An electromagnetic wave of freq = 3.0 MHz passes from vaccum into dielectric medium with permittivity e= 4.0 Then : a) wavelength is doubled and frequency remains same , b) wavelength is doubled and frequency becomes half c) wavelength is halved and frequenc remains unchanged d) both remain unchanged

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

Approved