Why are relatively low frequencies used in inspecting ferromagnetic materials?

Using relatively low frequencies for inspecting ferromagnetic materials is primarily due to the material's properties and the physical interactions involved in the inspection process. Ferromagnetic materials, such as iron and steel, have significant magnetic permeability, allowing lower frequency electromagnetic waves to penetrate more deeply without excessive attenuation.

When low frequency is employed, it becomes easier for the inspection techniques to assess deeper layers of the material and detect flaws that might be present beneath the surface. This deeper penetration capability is crucial for identifying defects or inconsistencies that could compromise the integrity of the material, making it essential in applications where safety and reliability are critical.

The other options, while they may have some relevance in different contexts, do not accurately capture the reason for using low frequencies in this specific case. Higher resolution, for instance, is more commonly associated with higher frequency inspections, which provide finer detail but less penetration, making it unsuitable for assessing deep flaws in ferromagnetic materials. Thus, the focus on the material’s penetrability and the effectiveness of low frequencies in facilitating deeper inspections is fundamental to understanding the choice of frequency in this context.