Surveying and Levelling

281. The lens equation 1/f = 1/ + 1/ is applicable

1. When the thickness of the lens is small
2. Only to conjugate distances along the principal axis
3. The computed quantities are accurate enough for geometrical optics of simple distances
4. All the above

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282. The limiting length of an offset does not depend upon

1. Accuracy of the work
2. Method of setting out perpendiculars
3. Scale of plotting
4. Indefinite features to be surveyed

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283. The line normal to the plumb line is known as

1. Horizontal line
2. Level line
3. Datum line
4. Vertical line

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284. The line of collimation method of reduction of levels, does not provide a check on

1. Intermediate sights
2. Fore sights
3. Back sights
4. Reduced levels

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285. The line of sight is kept as high above ground surface as possible to minimise the error in the observed angles due to

1. Shimmering
2. Horizontal refraction
3. Vertical refraction
4. Both shimmering and horizontal refraction

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286. The longitudinal section of the surface of bubble tube is

1. Straight
2. Circular
3. Parabolic
4. Elliptic

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287. The magnetic bearing of a line is 32° and the magnetic declination is 10° 15' W. The true bearing is

1. 21° 45'
2. 42° 15'
3. 42° 15' W
4. 21° 45' W

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288. The magnetic meridian at any point, is the direction indicated by a freely suspended

1. Magnetic needle
2. And properly balanced magnetic needle
3. Properly balanced and uninfluenced by local attractive force
4. Magnetic needle over an iron pivot

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289. The main plate of a transit is divided into 1080 equal divisions. 60 divisions of the Vernier coincide exactly with 59 divisions of the main plate. The transit can read angles accurate upto

1. 5"
2. 10"
3. 15"
4. 20"

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290. The main principle of surveying is to work

1. From part to the whole
2. From whole to the part
3. From higher level to the lower level
4. From lower level to higher level

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