Question

Light travels in the positive x-direction. At a particular location and time the electric field points in the positive y-direction. In which direction is the magnetic field?

a) positive z-direction

b) negative z-direction

Answer 1

As we know that the direction of light travel = direction of electric field $\times$ direction of magnetic field ('$\times$' denoted cross-product)

Here,

direction of light travel = positive x direction = + i

direction of electric field = positive y direction = + j

Therefore,

+i = +j $\times$ direction of magnetic field

==> direction of magnetic field = + k = positive z-direction ==> ANSWER-(a)