The speed of light in a given medium is given by,
v=μrϵrc
Magnetic field is B=μrμ0H.
Also, the relation between the magnetic field and electric field is given by,
E=vB⇒E=μrϵrc×μrμ0H=ϵrc×μr×μ0H⇒E=6.443×108×1.61×4π×10−7×4.5×10−2=8.48Vm−1