# Electromagnetic waves point to point propagation

• Stanley514
In summary, the conversation discusses the possibility of transferring electromagnetic waves in a lossless manner, similar to how electricity is transferred point to point. It is suggested that this could be helpful for wireless energy transfer. However, it is concluded that this is not currently possible due to diffraction and spreading of the energy. Various methods such as using large lenses or mirrors and directional antennas are discussed, but it is ultimately determined that lossless wireless energy transfer cannot be achieved at this time.
Stanley514
Is there a theoretical way to force electromagnetic waves transfere energy point to point like electricity instead omni-dirrectionally? I think it might be helpful for looseles wireless energy transfere.

Like a flashlight?

No. Waves suppose to go for any distance and walk around any obstacles without looses. They need to have some kind of an absolute diffraction. Light could propagate linearly, only.

Stanley514 said:
walk around any obstacles without looses

Sorry, but no.

Use fibre optics. It walks around all kinds of stuff.

stedwards said:
Use fibre optics. It walks around all kinds of stuff.
No. Need wireless.

Stanley514 said:
I think it might be helpful for looseles wireless energy transfere.

nothing is lossless, so no, you cannot do it

various RF antennas can be used to beam a large portion of the energy in a particular direction, but there is still lots of spreading out of the energy
and the longer the distance between the transmitter and receiver, the more the signal spreads out

so again, no, cannot be done in a lossless way

Dave

Stanley514 said:
Is there a theoretical way to force electromagnetic waves transfere energy point to point like electricity instead omni-dirrectionally? I think it might be helpful for looseles wireless energy transfere.
If we make the source of radiation, say a lens or concave mirror, large in size, the beam will be narrow, but will still diverge due to diffraction. At close distances, however, the beam is approximately parallel, and so the propagation between two mirrors can be nearly loss free. The distance for which the beam remains parallel is the Rayleigh Distance, and is approximately = Diameter^2 / (2 lambda). This distance also corresponds with the furthest point at which a lens or mirror may be focused.
davenn said:
nothing is lossless, so no, you cannot do it

various RF antennas can be used to beam a large portion of the energy in a particular direction, but there is still lots of spreading out of the energy
and the longer the distance between the transmitter and receiver, the more the signal spreads out

so again, no, cannot be done in a lossless way

Dave
As a matter of interest, if the distance between the lenses or mirrors is not too great, it is possible to have a parallel beam and to convey nearly all the energy. In the London Science Museum, they have an optical waveguide consisting of a long pipe with a sequence of lenses, so you can see small objects several metres away. The lenses or concave mirrors must be closer than the Rayleigh Distance, which is approximately,
= Diameter^2/(2 Lambda), and is the maximum distance at which a lens or mirror can form a focus. Optical waveguides like this were proposed for communication just before optical fibre became practicable.

Vanadium answered this fine with their second post. Just point a flashlight at a photovoltaic cell. Or use a laser if you want something better collimated.

Khashishi said:
Vanadium answered this fine with their second post. Just point a flashlight at a photovoltaic cell. Or use a laser if you want something better collimated.
The OP didn't want to use light

he hinted that he wanted to use RF ... hence why I went into directional antennas

## 1. What are electromagnetic waves?

Electromagnetic waves are a type of energy that can travel through space. They are created by the movement of electrically charged particles and consist of both electric and magnetic fields.

## 2. How do electromagnetic waves propagate?

Electromagnetic waves propagate through space by oscillating, or moving back and forth, in a perpendicular direction to each other. This movement creates a wave pattern that can travel through a vacuum or through a medium such as air or water.

## 3. What is point to point propagation?

Point to point propagation refers to the transmission of electromagnetic waves from one specific location to another. This can be achieved through various methods such as satellite communication, radio transmission, or fiber optic cables.

## 4. What are some applications of point to point propagation?

Point to point propagation has numerous applications, including long-distance communication, wireless internet, satellite TV and radio, remote sensing, and radar systems. It is also used in medical imaging, such as MRI machines, and in industrial processes, such as welding and heating.

## 5. How do electromagnetic waves travel in point to point propagation?

In point to point propagation, electromagnetic waves travel in a straight line from the transmitting point to the receiving point. This is known as line of sight propagation and requires an unobstructed path between the two points. In some cases, the waves may be reflected or diffracted, allowing them to reach their destination even if there are obstacles in the way.

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