50. The tangent to the liquid surface in a level tube, is parallel to the axis of the level tube at
A. every point of the bubble
B. either end of the bubble
C. the mid-point of the bubble
D. no where.
51. The sensitiveness of a level tube decreases if
A. radius of curvature of its inner surface is increased
B. diameter of the tube is increased
C. length of the vapour bubble is increased
D. both viscosity and surface tension are increased.
52. In a constant level tube, size of the bubble remains constant because uppe ? wall is
A. of relatively larger radius
B. of relatively smaller radius
D. convex downwards.
53. The line normal to the plumb line is known as
A. horizontal line
B. level line
C. datum line
D. vertical line.
54. In levelling operation,
A. The first sight on any change point is a back sight
B. The second sight on any change point is a fore sight
C. The line commences with a fore sight and closes with a back sight
D. The line commences with a back sight and closes with a foresight.
55. A relatively fixed point of known elevation above datum, is called
A. bench mark
B. datum point
C. reduced level
D. reference point.
56. The rise and fall method of reduction of levels, provides a check on
A. back sights
B. fore sights
C. intermediate sights
D. all of these.
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