·CE If the electric field in an electromagnetic wave is...

$\cdot$ CE If the electric field in an electromagnetic wave is increasing in
magnitude at a particular time, is the magnitude of the magnetic
field at the same time increasing or decreasing? Explain.

Key Concepts

Electromagnetic Waves

Electromagnetic waves consist of oscillating electric and magnetic fields that propagate through space. Their behavior is governed by Maxwell's equations, which allow the waves to travel even in a vacuum, with the fields continually regenerating each other.

In-Phase Relationship

In electromagnetic waves, the electric and magnetic fields oscillate in phase with one another, meaning that when one field is increasing, the other is likewise increasing at the same moment. This synchronous relationship is a direct consequence of the interdependent nature of the fields as described by Maxwell's equations.

Maxwell's Equations

Maxwell's equations describe how electric and magnetic fields are generated and altered by each other as well as by charges and currents. In the context of electromagnetic waves, the equations show that a time-varying electric field induces a time-varying magnetic field, and vice versa, ensuring that both fields increase or decrease together during the wave's propagation.

Transcript

00:01 Alright, so we've been asked if the electric field of an electromagnetic wave is increasing at some particular time, then what is the magnetic field doing? now, this is kind of a tricky question, but the example in our textbook is really talking about an antenna admitting an electromagnetic wave, emitting an electromagnetic wave.

00:28 So we're going to focus on that right now.

00:31 So if this is time and this is one direction that we'll call x, and this is a different direction that we'll call y, when an antenna is emitting electromagnetic radiation, what it's doing is that if the electric field looks something like this, so it's getting bigger with time, and then it's getting smaller with time, it's going to look something like this.

01:07 So this is our electric field.

01:10 Then the magnetic field has to propagate perpendicular to the electro, the electric field.

01:17 It's going to look something like this.

01:21 It's going to get bigger as the electric field gets bigger, and then it's going to get smaller as the electric field gets smaller.

01:30 All right, so this is our magnetic field.

01:35 Okay, so at for example this point in time when, or this point in time, when the electric field is increasing from time one to time two, the magnetic field is also increasing.

01:56 As the electric field decreases with time, the magnetic field is decreasing with time.

02:02 As the electric field gets super, super negative with time, it keeps going down.

02:10 The magnetic field also keeps getting more negative in the y direction.

02:16 So that's what happens when an electromagnetic wave is emitted from an antenna...

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