Question Video: Explaining the Huygens Wave Model of Electromagnetic Radiation | Nagwa Question Video: Explaining the Huygens Wave Model of Electromagnetic Radiation | Nagwa

Question Video: Explaining the Huygens Wave Model of Electromagnetic Radiation Physics • Third Year of Secondary School

Fill in the blanks: According to the Huygens wave model of electromagnetic radiation, an electromagnetic wave originates at a _ and moves in _ from the _.

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Video Transcript

Fill in the blanks. According to the Huygens wave model of electromagnetic radiation, an electromagnetic wave originates at a blank and moves in blank from the blank. (A) Surface, one direction, surface. (B) Point, all directions, point.

Our answer options give us two possible explanations for what’s called the Huygens wave model of electromagnetic radiation. This wave model actually applies not just to electromagnetic radiation but to all waves.

Say that we have a series of wave fronts like this propagating to the right. Note that these wave fronts are flat; they’re not curved lines but are straight. This means that whether we model the wave fronts as originating from a surface and moving in one direction from that surface, say forward in the direction of our waves propagation here, or whether we model the electromagnetic waves as originating from a point, say, for example, at this point here on this wave front, and then propagating out in all directions from that point, so long as we assume that all points along the wave front are equally sources of waves that move out in all directions, either one of these two different wave models can explain the wave propagation we see here.

However, let’s say that we pass these straight wave fronts through a small opening in a wall. When that happens, the pattern of wave fronts on the other side looks something like this. With these curved wave fronts, we can no longer say that both answers are valid in explaining how the wave moves along. If we consider our first answer option that this wave model describes waves originating at a surface, then we could imagine, say, this surface giving off another wave front. But the size of that wave front would be limited to the size of this surface. Even if that wave front did then move to the right as we see the wave fronts moving here, it wouldn’t be able to create the next wave front we see in the series. After all, these wave fronts we see are getting longer and longer.

What can produce these successive wave fronts though is if each point on each wave front is a source of other waves. If these waves then propagate out in all directions and interfere with one another, then in that case we can get the wave fronts we see here, which are broadening or widening out, we could say it, from this opening. This shows us that of the two descriptions given here, it’s description (B) that accurately tells us about the Huygens wave model of electromagnetic radiation. Our correctly completed sentence reads “According to the Huygens wave model of electromagnetic radiation, an electromagnetic wave originates at a point and moves in all directions from the point.”

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