# An EM waves is propagating in a medium with a velocity v = v î . The instantaneous oscillating electric field…

Q: An EM waves is propagating in a medium with a velocity v = v î . The instantaneous oscillating electric field of this EM waves is along +Y axis . Then the direction of oscillating magnetic field of the EM waves will be along

(a) -Y axis

(b) -X direction

(c) +Z direction

(d) -Z direction

Ans: (c)

Sol: For EM waves

$\displaystyle \vec{E} \times \vec{B} || \vec{v}$

$\displaystyle E \hat{j} \times \vec{B} || v \hat{i}$

$\displaystyle \vec{B} = B \hat{k}$