Question

Light waves are travelling along the y-direction. If the corresponding $\overrightarrow E$ vector at any time along the x−axis, the direction of $\overrightarrow B$ vector at that time is along
A) Y-axis
B) X-axis
C) Z-axis
D) –Z-axis

Answer 1

According to the question, it is given that light wave is travelling along y-direction and if the corresponding $\overrightarrow E$ vector at any time along the x−axis, then we need to calculate the direction of $\overrightarrow B$ vector at that time. Here we need to apply the concept that the light waves are electromagnetic in which $\overrightarrow E$ and $\overrightarrow B$ .

Complete step by step answer:
In physics, electromagnetic radiation refers to the waves of the electromagnetic field, propagating through space, carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, light, ultraviolet, X-rays, and gamma rays. All of these waves form part of the electromagnetic spectrum. Electromagnetic waves or EM waves are waves that are created as a result of vibrations between an electric field and a magnetic field. In other words, EM waves are composed of oscillating magnetic and electric fields. Electromagnetic waves are formed when an electric field comes in contact with a magnetic field. They are hence known as electromagnetic waves. The electric field and magnetic field of an electromagnetic wave are perpendicular (at right angles) to each other. They are also perpendicular to the direction of the EM wave.
Light wave is an electromagnetic wave in which $\overrightarrow E$ and $\overrightarrow B$ are at right angles to each other as well as at right angles to the direction of wave propagation. So from the given information in the question, the direction of the $\overrightarrow B$ vector is in the positive z direction.
So, the final answer is C) z-axis.

Note:
Heinrich Hertz was a brilliant German physicist and experimentalist who demonstrated that the electromagnetic waves predicted by James Clerk Maxwell actually exist. Hertz is also the man whose peers are honoured by attaching his name to the unit of frequency; a cycle per second is one hertz.