An imaginary line tangential to the longitudinal curve of the bubble tube at its middle point is called
A)axis of telescope
B)axis of level tube
C)level line
D)line of collimation

Question

Quizplus · Accepted Answer

The axis of the level tube is an imaginary line tangential to the longitudinal curve of the bubble tube at its middle point, representing the direction that is considered level for the purposes of the instrument's measurements.

An Imaginary Line Tangential to the Longitudinal Curve of the Bubble