Electomagnetic waves frequency and distance travelling relation

[aneesholv]

Hai


Can you tell how the frequency of an electromagnetic wave depends its travelling distance . Suppose two radio waves 90MHz and 80 MHz , which wave have the ability to travel more distance . Please explain the relation between frequency, energy .wavelength, power and
distance of an EM wave

Regards
Aneesh

 

[jeffrey samuel]

rayleigh's scattering law says so this holds the wave length and the amount of radiation scattered in diverse directions note it

 

[Element_115]

Hai


Can you tell how the frequency of an electromagnetic wave depends its travelling distance . Suppose two radio waves 90MHz and 80 MHz , which wave have the ability to travel more distance . Please explain the relation between frequency, energy .wavelength, power and
distance of an EM wave

Regards
Aneesh

Lower Frequencies travel better (They can bounce off the Ionosphere).
But, there is not much difference between 80 & 90 MHz.

 

[Mityan]

https://en.wikipedia.org/wiki/Friis_transmission_equation

Thats an elementary question. Very strange that you did not even take a single try to find anything on web by yourself

 

[ishailesh]

Hai


Can you tell how the frequency of an electromagnetic wave depends its travelling distance . Suppose two radio waves 90MHz and 80 MHz , which wave have the ability to travel more distance . Please explain the relation between frequency, energy .wavelength, power and
distance of an EM wave

Regards
Aneesh

Radio waves at different frequencies propagate in different ways.
In free space, all electromagnetic waves (radio, light, X-rays, etc.) obey the inverse-square law which states that the power density of an electromagnetic wave is proportional to the inverse of the square of the distance from a point source. Doubling the distance from a transmitter means that the power density of the radiated wave at that new location is reduced to one-quarter of its previous value.
The power density per surface unit is proportional to the product of the electric and magnetic field strengths. Thus, doubling the propagation path distance from the transmitter reduces each of their received field strengths over a free-space path by one-half.

At extra low frequencies (ELF) and very low frequencies the wavelength is very much larger than the separation between the earth's surface and the D layer of the ionosphere, so electromagnetic waves may propagate in this region as a waveguide. Indeed, for frequencies below 20 kHz, the wave propagates as a single waveguide mode with a horizontal magnetic field and vertical electric field.

Lower frequencies (between 30 and 3,000 kHz) have the property of following the curvature of the earth via groundwave propagation in the majority of occurrences.In this mode the radio wave propagates by interacting with the semi-conductive surface of the earth. The wave "clings" to the surface and thus follows the curvature of the earth.Since the ground is not a perfect electrical conductor, ground waves are attenuated rapidly as they follow the earth’s surface. Attenuation is proportional to the frequency making this mode mainly useful for LF and VLF frequencies.

Radio waves in the MF ranges may also propagate as ground waves, but suffer significant losses, or are attenuated, particularly at higher frequencies. But as the ground wave mode fades out, a new mode develops: the sky wave. Sky waves are reflections from the ionosphere. While the wave is in the ionosphere, it is strongly bent, or refracted, ultimately back to the ground. From a long distance away this appears as a reflection. Long ranges are possible in this mode also, up to hundreds of miles.

Line-of-sight is the direct propagation of radio waves.This is probably the most common of the radio propagation modes at VHF and higher frequencies.
Beyond VHF, all the propagation is line-of-sight. Communications are limited by the visual horizon.