The ratio of contributions made by the electric field and magnetic field components to the intensity of an EM wave is:

1. c : 1

2. c2 : 1

3. 1 : 1

4. c : 1

(c)
Hint: The energies of the electric field and the magnetic field are equal to each other in an electromagnetic wave.
Step 1: Find the energies of the electric field and the magnetic field.
Intensity in terms of electric field, Uav =12ε0E02
intensity in terms of magnetic field, Uav=B022μ0
Now taking the intensity in terms of electric field,
           (Uav)electric field=12ε0E02
                          =12ε0cB02              E0=cB0
                              =12ε0×c2B2
But,  c=1μ0ε0
 (Uav)electric field=12ε0×B2μ0ε0=Uavmagnetic field
Step 2: Find the ratio of intensities.
Thus, the energy in the electromagnetic wave is divided equally between the electric field vector and the magnetic field vector.
Therefore, the ratio of contributions by the electric field and magnetic field components to the intensity of an electromagnetic wave is 1: 1.