Magnetic field lines are more crowded towards the pole of the magnet because magnetic effect is more or the magnetic field lines are very strong towards the pole of a magnet.

Introduction:
Magnetic field lines represent the direction and strength of a magnetic field. They are used to visualize the magnetic field around a magnet. The pattern formed by the magnetic field lines depends on the shape and orientation of the magnet. In the case of a bar magnet, the magnetic field lines tend to be more closed at the poles.

Explanation:
The concept of magnetic field lines:
Magnetic field lines are imaginary lines used to represent the direction and strength of the magnetic field. They are drawn such that the tangent to the field line at any point gives the direction of the magnetic field at that point. The density of the field lines indicates the strength of the magnetic field, with denser lines representing a stronger field.

Magnetic field around a bar magnet:
When a bar magnet is placed in a magnetic field, it produces its own magnetic field. The magnetic field lines around a bar magnet emerge from one pole, called the north pole, and enter the other pole, called the south pole. The magnetic field lines form closed loops that extend from one pole to the other.

Concentration of magnetic field lines at the poles:
The magnetic field lines tend to be more closed at the poles of a magnet due to the following reasons:

1. Convergence of magnetic field lines: The magnetic field lines emerge from the north pole and converge towards the south pole. As they approach the poles, the field lines become more concentrated, resulting in a higher density of field lines. This concentration of field lines indicates a stronger magnetic field at the poles.

2. Uniform distribution of magnetic charge: The poles of a magnet can be considered as the regions where the magnetic charge is concentrated. Just like electric charges are concentrated at the poles of an electric dipole, the magnetic charge is concentrated at the poles of a magnet. The distribution of this magnetic charge causes the magnetic field lines to curve and form closed loops around the poles.

3. Attraction and repulsion: The closed loop nature of magnetic field lines at the poles is a consequence of the attractive and repulsive forces between magnets. Like poles repel each other, and therefore the magnetic field lines repel each other, causing them to form closed loops. On the other hand, opposite poles attract each other, resulting in the convergence of magnetic field lines towards the polar region.

Conclusion:
In conclusion, the magnetic field lines are more closed at the poles of a magnet due to the convergence of field lines, the distribution of magnetic charge, and the attractive and repulsive forces between magnets. This concentration of field lines at the poles indicates a stronger magnetic field in those regions. Understanding the pattern of magnetic field lines helps in visualizing and studying the behavior of magnetic fields.