Final answer:
The i term is neglected in optics because it represents the distance of an object that is at infinity. The thin-lens approximation assumes a very thin lens, allowing for simplified calculations. Neglecting the i term simplifies equations and makes the analysis of optics problems easier.
Step-by-step explanation:
In optics, the i term is neglected because it represents the distance of an object that is very far away from the lens. This is known as the object being at infinity. When the object is at infinity, the image distance and object distance become essentially equal, and the i term can be neglected in the thin-lens approximation.
In addition, the thin-lens approximation assumes that the lens is very thin compared to the other distances involved. This allows us to simplify the calculations and consider only the distance terms that significantly affect the image formation.
By neglecting the i term, we can simplify the equations and make the analysis of optics problems easier and more manageable.