A asked in Science & MathematicsPhysics · 6 years ago

# How do waves die off?

I need someone that can thoroughly explain to me in depth how waves die off. I know that WiFi at homes have only a certain radius you can be at until the signal dies off; however, I don't understand why. I also know that as you increase frequency, you have shorter wavelength; I'm confused about the energy part of the wave. I need information on how and why a radar wave (I'm not sure if radar is another type of wave or not, correct me if I'm wrong) only can travel a certain distance before you can no longer see any objects appear on the display. Please do not talk about interference, I want to know in a experiment where no outside factors are present, why a wave with a high frequency will die off as it travels farther.

If I have made no sense, let me tell you what I need for a requirement for my presentation.

My topic is about radars and how it relates to the Electromagnetic Spectrum.

The requirement I'm confused about is: I must include all valid relationships between wavelength, frequency and energy of my topic.

I already know wavelength and frequency, I'm just lost as to what to type or research about the energy of the radar waves (again, correct me if there are no such things as radar waves).

If you give me an acceptable answer to this problem, I will give you all the points I can give you; as another incentive: I could help you with any computer questions you may have too, if you'd like.

Thanks for viewing!

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• 6 years ago

The main reason e-m waves 'die off' (intensity weakens) with distance travelled is because they are spreading-out in every direction over the surface of an ever expanding sphere .. the energy associated with the wave is being continually 'thinned-out' as it's range increases.

As the area surface area of the expanding sphere depends on it's radius squared (A = 4πr²) .. doubling the distance waves travel (doubling the radius) increases the area by a factor of 4, reducing the wave intensity by 1/4 at any point.

The same happens in 2D as ripples spread-out from a source over the surface of a pond .. their intensity decreases as they travel and thin-out over a larger area.

E-M waves can also be absorbed by the atmosphere (including it's water vapour) as they travel .. this usually happens when the wave frequency matches a natural vibration frequency of electrons in the air molecules .. transferring energy from the wave to the molecule, so causing the wave energy to 'die-off;