A larger number of field lines crossing per unit area means the field is:

1. The spacing of field lines carries information as well as their direction. 2. Crowded lines mean something different from sparse ones. 3. The larger the number of field lines crossing per unit area, the stronger is the magnitude of the field. 4. So the field is stronger there. _Source: syllabus Physics Part I, Ch 5 'Magnetism and Matter'_