When you apply a magnetic field to a material it is observed that the magnetic field inside decreases. What material property have you observed?
a) Paramagnetism
b) Diamagnetism
c) Ferromagnetism
Try looking up the definitions of the answers. You should be able to find the answer.
b) Diamagnetism
The material property observed when the magnetic field inside a material decreases under the application of an external magnetic field is called diamagnetism. Diamagnetism is a property exhibited by all materials to some extent, and it is a result of the induced magnetic moments in atoms or molecules opposing the applied magnetic field.
To arrive at this answer, we can rule out paramagnetism and ferromagnetism as potential options. Paramagnetism is the property of some materials to align their magnetic moments in the direction of an applied magnetic field, resulting in an increased magnetic field inside the material. On the other hand, ferromagnetism is a property where certain materials exhibit strong magnetic behavior even in the absence of an external magnetic field. These materials can be strongly magnetized and retain their magnetization when the external magnetic field is removed.
Thus, by process of elimination, the correct answer is b) Diamagnetism.