An electromagnetic wave of frequency $$\upsilon = 3.0$$ MHz passes from vaccum into a dielectric medium with relative permittivity $${{\varepsilon _r}}$$ = 4.0. Then

The condition under which a microwave oven heats up a food item containing water molecules most efficiently is

The ratio of amplitude of magnetic field to the amplitude of electric field for an electromagnetic wave propagatting in vacuum is equal to

The electric field associated with an em wave in vacuum is given by
E = $$\widehat i$$ 40 cos (kz $$-$$ 6 $$ \times $$ 10⁸ t) where E, z and t are in volt/m, meter and seconds respectively. The value of wave vector k is