Light is an electromagnetic wave. Its speed in vacuum is given by the expression

The intensity of the light from a bulb incident on a surface is $0.22 \,W / m ^{2}$. The amplitude of the magnetic field in this light-wave is_______ $\times 10^{-9} \,T$. (Given : Permittivity of vacuum $\epsilon_{0}=8.85 \times 10^{-12} \,C ^{2} N ^{-1} m ^{-2}$, speed of light in vacuum $c =3 \times 10^{8} \,ms ^{-1}$ )

Figure given shows the face of a cathode-ray oscilloscope tube, as viewed from in front. $i.e.$ the electron beam is coming out normally from the plane of the paper. The electron beam passes through a region where there are electric and magnetic fields directed as shown. The deflections of the spot from the center of the screen produced by the electric field $E$ and the magnetic field $B$ separately are equal in magnitude. Which one of the diagrams below shows a possible position of the spot on the screen when both fields are operating?

Calculate the electric and magnetic fields produced by the radiation coming from a $100\; W$ bulb at a distance of $3\; m$. Assume that the efficiency of the bulb is $2.5 \%$ and it is a point source.

Write equation of energy density of electromagnetic waves.