What is Subtending? Definition, Examples, and Applications

Subtending is a term used in geometry and optics to describe the relationship between two objects or surfaces that are intersecting or overlapping. Specifically, if one object or surface (the "subtend" or "underlying surface") is partially covered by another object or surface (the "superimposed" or "overlying" surface), then we say that the superimposed surface subtends the underlying surface.

For example, if you hold up a small object (like a pen) in front of a larger object (like a piece of paper), the pen will subtend the paper, meaning that it will cover a portion of the paper's surface. The relationship between the two objects is one of overlap or covering, and the pen is said to be subtending the paper.

In optics, subtending is used to describe the angle of view of an optical instrument, such as a telescope or a microscope. The angle of view is the angle between the two surfaces that are intersecting, and it determines how much of the underlying surface can be seen from a given point of view. For example, if a telescope has a wide angle of view, it will subtend a larger portion of the sky than one with a narrower angle of view.

In summary, subtending is a term used to describe the relationship between two objects or surfaces that are intersecting or overlapping, and it is commonly used in geometry and optics to describe the angle of view of an optical instrument.