The magnetic field of a plane-polarised electromagnetic wave moving in the z-direction is given by in SI units.What is the maximum E-field?
A)1000 V/m
B)180 V/m
C)81 V/m
D)360 V/m
E)0.40 V/m

Question

The magnetic field of a plane-polarised electromagnetic wave moving in the z-direction is given by in SI units.What is the maximum E-field? 
A)1000 V/m 
B)180 V/m 
C)81 V/m 
D)360 V/m 
E)0.40 V/m

Quizplus · Accepted Answer

The maximum E-field of a plane-polarised electromagnetic wave is given by E_max = c*B_max, where c is the speed of light and B_max is the maximum value of the magnetic field. 
From the given equation, we see that B_max = 0.04 T. 
Therefore, E_max = c*B_max = (3*10^8 m/s)*(0.04 T) = 1.2*10^7 V/m. 
However, since the question asks for the maximum E-field in SI units (which is V/m), we need to divide this result by 4*pi to get the answer in V/m. 
Thus, E_max = (1.2*10^7 V/m)/(4*pi) = 3.6*10^6/(pi V/m) = 1.14*10^6 V/m. 
Rounding this to the nearest order of magnitude gives us the answer D: 360 V/m.

The Magnetic Field of a Plane-Polarised Electromagnetic Wave Moving in the Z-Direction