The magnetic field an electromangetic wave in a substance is given by ` B = ( 2 xx 10^(-6) T)` cos `[ pi ( 0.04 xx 10^7 t)]` . Find the electromagnetic wave speed.

Explanation

Comparing the given equation with the standard wave equation `B=B_0 cos ( omega t + k x)`
we have ` , omega = pi xx 10^7 rad // s and k =pi xx ( 0.04 ) m^(-1)`
` therefore ` speed of electromangetic wave in this medium is
` v=(omega )/(k) = 2.5 xx 10^8 m/s`