A $1.5 \,kW$ laser beam of wavelength $6400 \,\mathring A$ is used to levitate a thin aluminium disc of same area as the cross-section of the beam. The laser light is reflected by the aluminium disc without any absorption. The mass of the foil is close to ......... $kg$

A plane electromagnetic wave travels in a medium of relative permeability $1.61$ and relative permittivity $6.44$. If magnitude of magnetic intensity is $4.5 \times 10^{-2} \;Am ^{-1}$ at a point, what will be the approximate magnitude of electric field intensity at that point$?$

(Given : permeability of free space $\mu_{0}=4 \pi \times 10^{-7}\;NA ^{-2}$, speed of light in vacuum $c =3 \times 10^{8} \;ms ^{-1}$ )

The electric field in a plane electromagnetic wave is given by

$\overrightarrow{{E}}=200 \cos \left[\left(\frac{0.5 \times 10^{3}}{{m}}\right) {x}-\left(1.5 \times 10^{11} \frac{{rad}}{{s}} \times {t}\right)\right] \frac{{V}}{{m}} \hat{{j}}$

If this wave falls normally on a perfectly reflecting surface having an area of $100 \;{cm}^{2}$. If the radiation pressure exerted by the $E.M.$ wave on the surface during a $10\, minute$ exposure is $\frac{{x}}{10^{9}} \frac{{N}}{{m}^{2}}$. Find the value of ${x}$.

If a source is transmitting electromagnetic wave of frequency $8.2 \times {10^6}Hz$, then wavelength of the electromagnetic waves transmitted from the source will be.....$m$

Show that the radiation pressure exerted by an $EM$ wave of intensity $I$ on a surface kept in vacuum is $\frac{I}{c}$.

A plane electromagnetic wave of frequency $28 \,MHz$ travels in free space along the positive $x$-direction. At a particular point in space and time, electric field is $9.3 \,V / m$ along positive $y$-direction. The magnetic field (in $T$ ) at that point is