At a certain place on earth, the north tip of the magnetic needle of a dip circle placed in the plane of magnetic meridian points 60° below the horizontal. The horizontal component of the earth’s magnetic field is measured to be 0.16 G. The magnitude of the earth’s magnetic field at the location is:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 0.32 G
A dip needle in the magnetic meridian points along the earth’s total field, so the angle it makes with the horizontal is the angle of dip \( \delta = 60^\circ \). The horizontal component is the part of the total field along the horizontal, \( H = B\cos\delta \).
\( \displaystyle B = \frac{H}{\cos\delta} = \frac{0.16\,\mathrm{G}}{\cos60^\circ} = \frac{0.16\,\mathrm{G}}{0.5} = 0.32\,\mathrm{G} \)
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 – …
