Final answer:
The part of human eyes that gets tired is the ciliary muscle, which is responsible for changing the shape of the lens. Eye strain, headaches, and aching or burning eyes can occur when this muscle gets fatigued. Taking breaks and doing eye exercises can help relieve eye fatigue.
Step-by-step explanation:
In human eyes, the part that gets tired is the ciliary muscle, which is responsible for changing the shape of the lens to allow us to focus on objects at different distances. When you concentrate on close work for long periods, such as reading or using electronic devices, this muscle can get fatigued, leading to symptoms like eye strain, headaches, and aching or burning eyes. Taking breaks and practicing eye exercises can help alleviate eye fatigue.