Angle of dip at a place is $30^0$. If the vertical component of earth's magnetic field at that point is $7.5\times 10^{-5}T$. then the total magnetic field of earth at that point will be :
• A
$7.5\times 10^{-5}T$
• B
$1.5\times 10^{-4}T$
• C
$8.67\times 10^{-5}T$
• D
$1.5\times 10^{-5}T$

#### Solution

Vertical component of earth magnetic field:
$B_v = B sin\theta$
$B= \dfrac{B_v}{sin\theta}= \dfrac{7.5\times 10^{-5} }{sin 30^0}= 2\times 7.5 \times 10^{-5}$
$= 1.5 \times 10^{-4}T$