Light with an energy flux of $18 \;W / cm ^{2}$ falls on a nonreflecting surface at normal incidence. If the surface has an area of $20\; cm ^{2},$ find the average force exerted on the surface during a $30$ minute time span.

If ${\varepsilon _0}$ and ${\mu _0}$ are respectively, the electric permittivity and the magnetic permeability of free space. $\varepsilon $ and $\mu $ the corresponding quantities in a medium, the refractive index of the medium is

In a plane electromagnetic wave, the directions of electric field and magnetic field are represented by $\hat{ k }$ and $2 \hat{ i }-2 \hat{ j },$ respectively What is the unit vector along direction of propagation of the wave.

Sun light falls normally on a surface of area $36\,cm ^{2}$ and exerts an average force of $7.2 \times 10^{-9}\,N$ within a time period of $20$ minutes. Considering a case of complete absorption, the energy flux of incident light is.

An electromagnetic wave travelling in the $x-$ direction has frequency of $2 \times 10^{14}\,Hz$ and electric field amplitude of $27\,Vm^{-1}$ . From the options given below, which one describes the magnetic field for this wave ?