An electric bulb is rated as $200 \,W$. What will be the peak magnetic field ($\times 10^{-8}\, T$) at $4\, m$ distance produced by the radiations coming from this bulb$?$ Consider this bulb as a point source with $3.5 \%$ efficiency.

The electromagnetic waves do not transport

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?

The average value of electric energy density in an electromagnetic wave is :

For a plane electromagnetic wave, the magnetic field at a point $x$ and time $t$ is

$\overrightarrow{ B }( x , t )=\left[1.2 \times 10^{-7} \sin \left(0.5 \times 10^{3} x +1.5 \times 10^{11} t \right) \hat{ k }\right] T$

The instantaneous electric field $\overrightarrow{ E }$ corresponding to $\overrightarrow{ B }$ is : (speed of light $\left.c=3 \times 10^{8} ms ^{-1}\right)$

A velocity selector consists of electric field $\overrightarrow{ E }= E \hat{ k }$ and magnetic field $\overrightarrow{ B }= B \hat{ j }$ with $B =12 mT$.

The value $E$ required for an electron of energy $728 eV$ moving along the positive $x$-axis to pass undeflected is:

(Given, , ass of electron $=9.1 \times 10^{-31} kg$ )