At 15cm, you measure a magnetic field of about 1.5 mT. If the magnetic field of a permanent magnet is dipole-like in this region, what is the closest magnetic field you would expect to measure at 30cm from the magnet?

closest magnetic field is  0.2 MT

Explanation:

given data

B = 1.5 mt

r = 30 cm

solution

as here magnetic filed due to magnetic dipole is inversely is inversely proportion to distance cube  that is

B ∝    ................1  

heer r1 is 15 cm and r2 is 30 cm

so magnetic field is

solve we get

B2 = 0.2 MT

explanation:

newton's third law, for every action there is an equal and opposite reaction.