A magnetic needle oscillates in a horizontal plane with a period T at a place where the angle of dip is 600. When the same needle is made to oscillate in a vertical plane coinciding with the magnetic meridian, its period will be
T1×1√BH1
Now, BH)2=BH1cos600
T1T2=√BH2BH1
T1T2= ⎷BH1cos600BH2
T2=√2T1