The refractive index of the ionosphere is ........

For a given electromagnetic wave,the magnitude of the electric field is $6.6 \,V \,m^{-1}$ at a point in space. The magnitude of the magnetic field at this point is . . . . . . $T$.

About $5 \%$ of the power of a $100 \; W$ light bulb is converted to visible radiation. What is the average intensity of visible radiation
$(a)$ at a distance of $1 \; m$ from the bulb?
$(b)$ at a distance of $10 \; m$? Assume that the radiation is emitted isotropically and neglect reflection.

If an electromagnetic wave is propagating in the $x$-direction and the electric and magnetic fields are in the $y$ and $z$-directions respectively,then write the equations for $E_y$ and $B_z$.

Which of the following statements is incorrect?

In a plane electromagnetic wave,which of the following has/have a zero average value in one complete cycle?
$(a)$ Magnetic field
$(b)$ Magnetic energy
$(c)$ Electric field
$(d)$ Electric energy