question_answer

A magnetic compass needle oscillates 30 times per minute at a place where the dip is \[45{}^\text{o},\]and 40 times per minute where the dip is \[30{}^\text{o}\]. If \[{{B}_{1}}\]and \[{{B}_{2}}\]are respectively the total magnetic field due to the earth at the two places, then the ratio \[{{B}_{1}}/{{B}_{2}}\]is best given by: [JEE Main Held on 12-4-2019 Morning]

A) 2.2

B) 1.8       

C) 0.7

D) 3.6

Correct Answer: C

Solution :

[c]