To keep the surveying instruments in fit condition
- Athe instrument should be removed and placed quickly in the box
- Bthe tripod legs should be set too close to each other and should be planted firmly on the ground
- Cwhen the magnetic needle of the instrument is in use, it should be raised off the pivot
- Dthe objective and eyepiece lens should not be touched with fingersCorrect
Solution
Concept
Care of surveying instruments
Step-by-step solution
1. Lenses must not be touched with fingers (grease and scratches). 2. Instruments should be removed carefully, tripod legs spread well apart, and the compass needle lifted off the pivot when NOT in use.
Explanation
Touching optical surfaces leaves marks that impair the view. The other statements are incorrect practice.
Why the other options are wrong
(a) rough handling damages the instrument; (b) legs set too close make the tripod unstable; (c) the needle is lifted off the pivot when it is not in use.
Shortcut
Do not touch the lenses.
Common mistake
Choosing (c).
Correct answer: D) the objective and eyepiece lens should not be touched with fingers