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To make a wave, it's necessary to have an oscillating source. This source needs eneergy to operate, and the longer it operates the more energy it uses. Longer waves take more time to form, therefore they have more energy than shorter ones. For example, wave A has more energy than wave B:Wave A is long and wave B is short

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    $\begingroup$ Need the context. What are the boundaries of these longer and shorter waves? Are these waves in water or air or some such? $\endgroup$
    – Dan
    Commented Feb 4, 2022 at 19:06
  • $\begingroup$ I was thinking of light waves when I made the question, but I think the same principles should apply for all waves. As for the boundaries, both waves have the same frequency and amplitude, A is 3.5 wavelenghts long and B is 2. $\endgroup$
    – Guilherme Mendonça
    Commented Feb 4, 2022 at 20:01
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    $\begingroup$ You can just look it up in most textbooks, v.g. Halliday-Resnick-Walker $\endgroup$
    – ZeroTheHero
    Commented Feb 4, 2022 at 20:06
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    $\begingroup$ Length matters, but so does amplitude. A higher amplitude with shorter duration could have more energy than a much longer duration with smaller wavelength. Energy is roughly proportional to the square of the amplitude and the duration. $\endgroup$
    – R. Romero
    Commented Feb 4, 2022 at 21:14
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    $\begingroup$ All things being equal it is generally true that longer waves contain more energy; but in most discussion, that is so built into the the assumptions of the discussion that it usually not stated. For example, in talking about the "energy of ocean waves" or the "energy of a radio wave" etc, people are usually not talking about since oceans first formed on the earth or since the radio station started broadcasting, but instead mean energy per unit time, or something like that. $\endgroup$
    – tom10
    Commented Feb 4, 2022 at 22:53

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Yes. If a radio transmitter for example works for 10s, or if it works for 100s, emitting the same frequency and amplitude, it needs 10 times more energy in the second case.

For EM waves the energy per volume is $$w = \frac{1}{2}(E^2 + B^2)$$. There is more energy for a wave packet with more volume.

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