Given equation of wave
→E=→E0(4×→10x−50t)
Comparing with general equation of wave,
→E=→E0(kx−wt),
we get,
w=50 rad/s. k=4×10−7m−1
Thus velocity of wave,
v=wk=504×10−7=1.25×108m/s
so, refractive index of medium,
μ=ev=3×1081.25×108=2.4
using,
u2=km.ke [km and ke are magnetic and dielectric di - constants]
as medium is non diamagnetic, km=1
⇒ke=μ2=(2.4)2⇒ke=5.76