[jimster]

We know that light diffracts, that it does not travel straight through an edge between different materials and that P900s don't give exact RE or FE results because the light is bending.

Do radio waves have the same problem?

On FE, if I sight something through a telescope and a radar set, could it be in some other position than where it appears due to bending of both radio and light waves in the same way?

[QED]

We know that light diffracts, that it does not travel straight through an edge between different materials and that P900s don't give exact RE or FE results because the light is bending.

Do radio waves have the same problem?

On FE, if I sight something through a telescope and a radar set, could it be in some other position than where it appears due to bending of both radio and light waves in the same way?

It absolutely can travel straight through without diffracting. Snell’s law demonstrates this!

[some_engineer]

We know that light diffracts, that it does not travel straight through an edge between different materials and that P900s don't give exact RE or FE results because the light is bending.

Do radio waves have the same problem?

On FE, if I sight something through a telescope and a radar set, could it be in some other position than where it appears due to bending of both radio and light waves in the same way?

Yes and it depends on what you are measuring. Radiowaves and light are both waves in the electromagnetic spectrum and for most materials except metamaterials and metals the refractive index of light also applies to radio waves.

The concept of ground waves is an example of radio-waves bending allthough I'm sceptical of their existence since they seem to be equally well explained by reflections off a non-perfect reflecting surface. These 'seem' to predict much better the transition of the path loss exponent from 20dB per decade to 40dB per decade in the far field via a 30dB per decade region which isn't predicted by ground waves but is measured.

A better example would be the refraction of radio waves by the upper atmosphere. Here we very clearly know we can have long range radiowave propagation due to the signals being bend by the gradually varying complex dielectric permeability of the sky.

[markjo]

We know that light diffracts, that it does not travel straight through an edge between different materials and that P900s don't give exact RE or FE results because the light is bending.

Do radio waves have the same problem?

On FE, if I sight something through a telescope and a radar set, could it be in some other position than where it appears due to bending of both radio and light waves in the same way?

I think that you mean refraction (light bending), not diffraction (light spreading out).  Any form of EM radiation, including light and radio, is subject to refraction when traveling between media of differing optical densities.