Question

The magnetic bearing of the sun for a location at noon is $183^\circ 30'$. If the sun is exactly on the geographic meridian at noon, the magnetic declination of the location is \underline{\hspace{1.5cm}.}

• A. $3^\circ 30'$ W
• B. $3^\circ 30'$ E
• C. $93^\circ 30'$ W
• D. $93^\circ 30'$ E

Hint:

Always compare true bearing vs magnetic bearing.
- If magnetic bearing $>$ true bearing $\Rightarrow$ declination is west.
- If magnetic bearing $<$ true bearing $\Rightarrow$ declination is east.

Answer 1

The Correct Option is A

Step 1: Recall the definition of magnetic declination.
Magnetic declination is the angle between the true north (geographic meridian) and the magnetic north (magnetic meridian). It is taken as east if magnetic north lies to the east of true north, and west if it lies to the west.

Step 2: Interpret the given data.
At noon, the sun is on the true meridian (true bearing $=180^\circ$).
But the observed magnetic bearing of the sun is $183^\circ 30'$.
This means the magnetic south line lies $3^\circ 30'$ west of the true south line.

Step 3: Relating to north.
If the magnetic south is west of the true south, then correspondingly the magnetic north must be west of the true north.
Hence, the magnetic declination is $3^\circ 30'$ W.
\[ \boxed{\text{Magnetic declination = } 3^\circ 30' \text{ W}} \]