Because when 2 ends of magnet meet if they are similar they will repel and we will easily get to know that they are either N-N or S-S

Repulsion

Repulsion is the surest test of magnetism because it is a unique property of magnets. When two magnets are brought close to each other, they can either attract or repel each other.

Explanation

- When two magnets repel each other, it indicates that they have like poles facing each other. This is a characteristic property of magnets and helps in identifying the presence of magnetism.
- Repulsion is a more reliable test compared to attraction because some materials that are not magnetized can still be attracted to magnets due to their magnetic properties.
- By observing repulsion between two magnets, we can confirm the presence of magnetism in the materials.

Significance

- Repulsion is a fundamental property of magnets and plays a crucial role in various applications of magnetism such as in magnetic levitation, magnetic resonance imaging (MRI), and electric motors.
- Understanding repulsion helps in distinguishing between magnetic and non-magnetic materials, which is essential in various scientific and technological fields.

In conclusion, repulsion is the surest test of magnetism as it is a unique property of magnets that helps in identifying the presence of magnetism in materials.