The imaginary lines joining the two poles of a magnet are called:
magnetic lines
connecting axis
magnetic axis
Hence, options (b) and (c) are correct.
The imaginary line connecting the pole and the focus of a curved mirror is called its longitude.
Two magnetic poles of pole strengths 324 mA−m and 400 mA−m. are kept at a distance of 10 cm in air. The null point will be at a distance of ––––––––– ( in cm ), on the line joining the two poles, from the weak pole if they are like poles :