Question Video: Identifying the Property of Electromagnetic Radiation the Defines Its Place in the Electromagnetic Spectrum | Nagwa Question Video: Identifying the Property of Electromagnetic Radiation the Defines Its Place in the Electromagnetic Spectrum | Nagwa

# Question Video: Identifying the Property of Electromagnetic Radiation the Defines Its Place in the Electromagnetic Spectrum Physics • Third Year of Secondary School

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Which of the following is a property of electromagnetic waves that defines which part of the electromagnetic spectrum they are part of? [A] Frequency [B] Amplitude [C] Speed

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### Video Transcript

Which of the following is a property of electromagnetic waves that defines which part of the electromagnetic spectrum they are part of? (A) Frequency, (B) amplitude, (C) speed.

If we think about an electromagnetic wave, we recognize that it has all three of these properties. The wave moves along at a speed equal to the speed of light in vacuum. The wave has an amplitude that is a maximum displacement from equilibrium. And it also has a frequency, which tells us how many cycles of the wave pass a given point every second. Since an electromagnetic wave does have all three of these properties, the question is, which of these properties is the one that defines which part of the electromagnetic spectrum the wave is a part of?

Interestingly, in vacuum, all electromagnetic waves move at the same speed. That means that wave speed can’t be the property that differentiates one wave from another. Wave amplitude though can vary between waves, and it’s related to the property of wave intensity. Even though wave amplitude can vary, it’s not the property by which electromagnetic waves are divided up on the electromagnetic spectrum. Rather, that happens according to a wave’s frequency. As we said, this is the number of cycles of the wave that pass a given point every second. A wave with relatively higher frequency but the same amplitude would look like this, while an electromagnetic wave with relatively lower frequency but the same amplitude could look like this.

We choose then answer option (A). Frequency is the property of electromagnetic waves that defines which part of the electromagnetic spectrum a wave is a part of.

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