Light waves are described as electromagnetic waves by Maxwell's equations and are characterized by three vector quantities: electric field, magnetic field, and the speed and direction of propagation of the energy of the wave. Which of the following statements is true about the relationship between the three vector quantities mentioned above for electromagnetic waves? a. The E field and B field oscillate parallel to one another and parallel to the propagation vector, as well. b. Whereas the E and B fields are always perpendicular to one another, the E field is at all times either parallel or anti-parallel to the propagation vector. c. The E and B fields oscillate perpendicular to one another, and both are orthogonal to the propagation vector. d. Whether the E field, B field, and propagation vector are parallel or orthogonal to one another depends on the polarization of the light wave.

option C

Explanation: When an electromagnetic wave is traveling in space, the electric field is always perpendicular to the magnetic field, which in turn are both perpendicular to the direction of propagation (velocity of the wave).

Let us consider an electric field in the y axis (Ej) and a magnetic field in the z axis (Bk) where j and k are unit vector.

Please note both magnetic field (B) and electric field (E) are perpendicular ( as we can see one is on the y axis and the other on the z axis which are known to be orthogonal, that's perpendicular).

The velocity of an electromagnetic wave is given as

v = Ej × Bk

We need to get the direction of the velocity so we use cross (vector) product to multiply the direction(unit vector)

j × k = i, which implies that the velocity is on the x axis.

Direction of velocity is x axis (i)

Direction of magnetic field is z axis (k)

Direction of electric field is y axis (j)

i, j and k are known to be perpendicular or orthogonal thus making the velocity, magnetic field and electric field of an electromagnetic wave perpendicular to each other.

This point validates option C