Question

question 98 of 100 · multiple choice

_ is the apparent movement of the crosshairs in an optical instrument, when the viewers head is moved. this condition is caused by an optical telescope that is not properly focused?

a collimation

b optical plummet

c offset

d parallax

Explanation:

Identify the optical phenomenon

The question describes the apparent movement of the crosshairs relative to the target in an optical instrument when the viewer's eye or head moves. This occurs when the image of the target does not fall on the same plane as the crosshairs due to improper focusing.

Evaluate the given options

• collimation: The process of aligning the optical axis of an instrument.
• optical plummet: A device used to position an instrument vertically over a reference point.
• offset: A perpendicular distance measured from a reference line.
• parallax: The apparent displacement or difference in the apparent position of an object viewed along two different lines of sight, which in optical instruments is eliminated by proper focusing.

Answer:

• (A) collimation
• (B) optical plummet
• (C) offset
• (D) parallax (Correct answer)