At a place the angle of dip is 30°. If the horizontal component of the earth's magnetic field is \( B_{H} \), the total magnetic field of the earth will be:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \( 2B_{H}/\sqrt{3} \)
The total field B of the earth makes the angle of dip \( \delta \) with the horizontal, and its horizontal component is \( B_H = B\cos\delta \).
\( \displaystyle B = \frac{B_H}{\cos\delta} = \frac{B_H}{\cos30^{\circ}} = \frac{B_H}{\sqrt{3}/2} = \frac{2B_H}{\sqrt{3}} \)
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Magnetic Declination and Dip – …
