What does my teacher mean when he says that all electromagnetic waves travel at the very same speed when travelling through a vacuum? If friend may, you re welcome answer as basic as possible.

You are watching: At what speed do electromagnetic waves travel in a vacuum


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Electromagnetic waves encompass visible light, radio waves, X-rays, and so on. What distinguishes these different bands of light is their frequency (or wavelength). Yet what castle all have in typical is the they take trip at the very same speed in vacuum.

The factor for qualifying "in vacuum" is because EM tide of different frequencies frequently propagate at various speeds through material.

The speed of a wave $c$, the wavelength $lambda$ and also frequency $f$ room all connected according to $c=lambda f$. For this reason if $c$ is the very same for every EM waves, climate if you (say) double the frequency of a wave, its wavelength will certainly halve.


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Assume you are walking under the road. You carry a small stick v you. Just for fun you decide to wiggle the stick rhythmically up and down at the rate of one up/down wiggle per second (you are a little of one olympic professional at rod wiggling so it"s really accurate and also reliable). Her stick wiggling is in ~ 1Hz. The rate at which girlfriend walk under the road is not pertained to the price at which friend wiggle the stick. You have the right to walk under the roadway at any type of speed you like and also still wiggle in ~ 1Hz.

Have you obtained it now ?

The speed of transmission of an e-m tide is not related to the frequency/wavelength.


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Not true. Negative analogy. First, in your last sentence you"re utilizing frequency and also wavelength synonymously, which they"re not. Frequency is the (oscillation rate) in a photon particle. Like the waving the the stick, it"s frequency is constant. Yet wavelength is a measure of frequency in ~ the border of speed. If frequency is a constant, and speed changes, then the wavelength need to change. So, frequency isn"t affected by speed, however wavelength is. The stick example shows the frequency constant, however not wavelength. A rollercoaster track example shows the wavelength constant. If a rollercoaster slow down, that still calls for it to move through the same route to obtain to the following crest. It"ll take much more time to obtain there, but the wave is still the same shape and also distance. However in order because that this to work, it"s frequency or energy decreases. In the wave fragment world, this doesn"t happen. Therefore, the rollercoaster instance shows united state the wavelength as a consistent only for theoretical purposes, but doesn"t work in the organic wave particle world. Just a particles power or frequency is constant. This dictates the speed and also wavelength have the right to change.

With that established. Let"s look in ~ the scenario of photons traveling with a vacuum. In a vacuum, over there is nothing to disrupt the speed. If the speed is continuous and we have currently established the frequency is constant, then the wavelength that that fragment is also a constant.

Now if we introduce matter. This reasons the particle"s rate or trajectory, or both to it is in altered. Changing the rate will change it"s wavelength. Changing it"s trajectory will reason it"s wavelength to go to zero in that direction. In both instances, energy is transferred and released, which provides rise to the idea that a photon is a particle. However at the exact same time, once it is complimentary to travel uninhibited again in a vacuum, it reverts earlier to it"s very same wavelength and also speed, i m sorry is properties of a pure wave.

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This ide of a photon gift a wave, is why we think it has to have the exact same speed in a vacuum. The straightforward answer is that we don"t really understand why they all take trip at the same speed. Every we understand is that this is a characteristics of a wave kind of energy. As with mass is a properties of a particle. It just is.