The magnetic field between two magnets, specifically between the north pole of one magnet and the south pole of another, follows the inverse square law as they move apart. This means that the strength of the magnetic field decreases as the distance between the magnets increases.
The reason for this decrease in magnetic field strength is primarily due to the distribution and alignment of magnetic field lines. Magnetic field lines originate from the north pole of a magnet and terminate at its south pole. These field lines form a continuous loop from one magnet to the other.
As the magnets move apart, the magnetic field lines spread out over a larger area. The same amount of magnetic flux, or the total number of field lines passing through a given area, is now distributed over a larger area. Therefore, the magnetic field strength (magnetic flux per unit area) decreases because the same amount of flux is spread out over a larger area.
This behavior is analogous to light spreading out as you move away from a source. The same amount of light is spread out over a larger surface area, resulting in decreased intensity. Similarly, the magnetic field strength decreases as the magnets move apart because the same amount of magnetic flux is distributed over a larger area.
It's important to note that the inverse square law applies specifically to the situation of point-like magnetic sources (idealized magnetic monopoles). In reality, magnets have complex field patterns and are better described by a combination of magnetic dipoles and multipole moments. Nevertheless, the inverse square law provides a good approximation for understanding the general behavior of the magnetic field between two magnets as they move apart.