Final answer:
The solid angle of a detector is determined by its geometric relationship with the source and does not depend on its depth.
Step-by-step explanation:
The solid angle of a detector does not depend on its depth. Solid angle is a measure of the amount of three-dimensional angular space that an object subtends at a point, usually measured in steradians (sr). It is solely dependent on the geometric relationship and the position between the detector surface and source, not the depth or thickness of the detector itself.
An example would be a camera lens; changing the depth of the lens does not affect the field of view it captures, it's rather the lens's diameter and the distance from the object that determines the solid angle.