The magnetic field induced at the centre of an orbit due to an electron revolving in the nth orbit of hydrogen atom is given by B=µ0in∕(2rn) Where in is the current in the nth orbit rn the nth orbit and µ0 the magneticpermeablity of free space. rn∝n2 in∝n−3 Therefore β∝n−5 So the answer is n−5 .