From the following image, why do we still call it isotropic? if the density at A and B differ, I don't think it's enough to call it isotropic. In my opinion, material is only isotropic if when we choose some point, around it in all directions, properties are the same throughout the end of the material from that point, but image taken from here, still says material is isotropic.
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the answers here are relevant https://physics.stackexchange.com/q/191543/ – anna v Sep 13 '23 at 10:35
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For a system to be isotropic w.r.t. a point of reference it has to appear the same in all directions. Say if I'm located at a point $p$ and from there I find the system isotropic then this just means that the system has the same property at a fixed radius $r$. In particular, it does not need to have the same properties everywhere but only on concentric shells.
A system that has the same property everywhere whould instead be homogeneous.
S.G
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Then we must say: material is isotropic with respect to point P with respect to radius $r$. – Giorgi Lagidze Sep 13 '23 at 11:59
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@GiorgiLagidze it doesn't have to be some fixed $r$. Think about the electric field $E \propto 1/r^2$. It is isotropic w.r.t. the charge at all values of $r$ although $E$ is different at all $r$'s. – S.G Sep 13 '23 at 12:35