How much does electromagnetic waves decay in seawater?

In water, it does not decay linearly, it decays exponentially, and the decay is very fast. The shorter the wavelength, the greater the attenuation; Electrical conductivity of water.

The higher it is, the greater the attenuation.

To make a comparison, the attenuation in the atmosphere is usually only decibel megameters, while in the seawater the attenuation is decibel meters.

The depth to which a long wave can penetrate water is a few meters, the depth of a very long wave is 10 to 20 meters, and the depth of a longer wave is 100 200 meters.

So underwater communications are made of long waves. It really doesn't work, you can only make sonar.

The centimeter wave has a shorter wavelength, which is equivalent to urinating on a steelmaking furnace, and it is gone as soon as it is spilled.

In engineering, the skin depth δ is often used to characterize the skin degree of electromagnetic waves, which is defined as the amplitude attenuation of electromagnetic waves to 1 exp (or the distance propagated by electromagnetic waves) of the surface value

Its size δ=1 ( *f* *f is the electromagnetic wave frequency is the relative permeability of seawater, where 1 is the conductivity of seawater, you can calculate it yourself through the above formula

The energy of the electromagnetic wave, if the vacuum is 1, then the electromagnetic wave into the seawater should be 9 16. Because the velocity of an electromagnetic wave in seawater is 3 4 in a vacuum, and the energy is proportional to the square of the velocity.

The attenuation formula for electromagnetic waves in the sea can be expressed by the following formula:

a = 10 * log10(i0 i) where a is the attenuation of the electromagnetic wave in seawater (in db), i0 is the intensity of the electromagnetic collapse wave at the incident point, and i is the intensity of the electromagnetic wave after passing a certain distance in the nuclear space during propagation.

This formula shows that the electromagnetic waves propagating in seawater gradually decay as the travel distance increases. Specifically, when the transmission distance increases, the signal loss is increasing due to the accumulation of the energy absorption and scattering of the electromagnetic field by seawater. Therefore, it is necessary to take into account this signal loss when designing long-distance communication or control systems, and take corresponding measures to ensure the quality and reliability of communication.

It is important to note that the above formula only applies to approximate calculations at low frequencies (below 20kHz). For high-frequency cases, more complex and accurate models are required for calculations.

Electromagnetic waves have different propagation characteristics in water than in air. Seawater has a strong absorption effect on electromagnetic wave energy, but it is different for electromagnetic waves of different wavelengths. The shorter the wavelength and the higher the frequency, the greater the attenuation in seawater.

Therefore, the attenuation of short waves in water is very fast and can hardly propagate through seawater, while the attenuation degree of long waves, very long waves, and ultra-long waves with longer wavelengths in seawater is much smaller, and they can enter the water of tens to hundreds of meters.

Very long wave communication is a radio communication with a wavelength of 100,000 meters (frequency of 3 30 kHz), also known as very low frequency communication. The transmission attenuation of very long waves in seawater is small, and the depth of entry into the water can be up to 20 meters.