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Physics Lesson 12.1.3 - Why is Light an Electromagnetic Wave? What does EM Wave Really Mean?
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Welcome to our Physics lesson on Why is Light an Electromagnetic Wave? What does EM Wave Really Mean?, this is the third lesson of our suite of physics lessons covering the topic of Features of Light, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
Why is Light an Electromagnetic Wave? What does EM Wave Really Mean?
Light, as a kind of EM wave carries energy, not matter. As such, it is produced by a source which when it is very hot becomes incandescent (emits light). Light is part of EM spectrum, i.e. unlike mechanical waves, it possesses both an electric and magnetic component (E and H) which are perpendicular to each other. These components are represented by the respective fields (electric and magnetic field). Thus, all EM waves contain two sinusoidal equations: one for each field. They are:
for electric field and
for magnetic field.
The electric field component is much greater than the magnetic one. The ratio between them gives the speed of light c.
The value 3 × 108 m/s for the speed of light in vacuum is a rounded value. Accurate measurements give the value c = 299 792 458 m/s.
The figure below shows the two components of EM wave where the magnetic component is much greater than it really is for demonstration purpose.
This is the reason why light is an EM wave, i.e. because it is a combination of an electric and magnetic sinusoidal component.
You have reached the end of Physics lesson 12.1.3 Why is Light an Electromagnetic Wave? What does EM Wave Really Mean?. There are 6 lessons in this physics tutorial covering Features of Light, you can access all the lessons from this tutorial below.
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