1. The line of sight is also called _____
a) line of telescope
b) line of centre of axis
c) line of collimation
d) line of objective
Explanation: The line of sight is a line which passes through the optical centre of the objective and the intersection of cross hairs. This is also called line of collimation.
2. What is the line which passes through the optical centres of objective and eye piece?
a) axis of the telescope
b) centre of axis line
c) line of collimation
d) line of objective
Explanation: The axis of the telescope is the line which passes through the optical centres of objective and eye piece.
3. The eyepiece magnifies the cross hairs.
a) True
b) False
Explanation: The cross hairs are placed in front of the eyepiece and in the plane where the real inverted image is produced by the objective. Thus, the eyepiece magnifies the cross hairs also.
4. The focal length of an objective varies with eyepiece.
a) True
b) False
Explanation: The focal length of an objective is constant. Focal length is independent to the particular lens
5. The establishment of line of sight, therefore, involves the following two essential conditions, the real image must be formed in front of the eyepiece, the plane of the image must coincide with that of the cross hairs.
a) True
b) False
Explanation: The establishment of a line of sight, therefore, involves the following two essential conditions, the real image must be formed in front of the eyepiece, the plane of the image must coincide with that of the cross hairs
6. The operation of forming or bringing the clear image of the object in the plane of cross hairs is known as ______
a) Centering
b) Adjusting
c) Parallax correcting
d) Focusing
Explanation: For quantitative measurements, it is essential that the image should always be formed in the fixed plane in the telescope where the cross hairs are situated. The operation of forming or bringing the clear image of the object in the plane of cross hairs is known as focusing.
7. By balancing back sight and fore sight error due to curvature can be eliminated.
a) True
b) False
Explanation: When the difference in elevation between any two points is determined from a single set up back sighting on one point and fore sighting on the other, error due to curvature can be eliminated. Error due to refraction also be eliminated.
8. By balancing back sight and fore sight error due to non parallelism of the line of collimation can be eliminated.
a) True
b) False
Explanation: When the difference in elevation between any two points is determined from a single set up back sighting on one point and fore sighting on the other, error due to non parallelism of the line of collimation can be eliminated. Error due to refraction also is eliminated.
9. By which of the following, the difference in elevation between two points can be calculated by taking a difference between the two readings and no correction for the inclination of the line of sight is necessary?
a) Levelling
b) Centering
c) Contouring
d) Balancing
Explanation: If the back sight and foresight distances are balanced, the difference in elevation between two points can be directly calculated by taking a difference of two readings and no correction for the inclination of the line of sight is necessary.
10. If the observed back sight and fore sight are x1 and x2. The correction back sight on A will be equal to x1-y1, where y1= D1 tan i°. The correct fore sight on B will be equal to x2-y2 where, y2 = D2 tan i°. Then what is the correction difference in level between A and B.
a) x1 – x2
b) x2 – x1
c) x1 – x2 + (D2 tan i° – D1 tan i°)
d) x2 – x1 + (D1tan i° + D2 tan i°)
Explanation: The correct difference in level between A and B is (x1 – x2) – (x2 – y2) = (x1 – x2) + (y2 – y1) = x1 – x2 + (D2 tan i° – D1 tan i°).