What does visual inspection primarily involve?

Visual inspection primarily involves checking for defects by eye. This technique is essential in quality control processes across various industries, as it allows inspectors to identify flaws, irregularities, or any inconsistent features in a product or component that may affect its functionality or quality. By using the human eye to assess the visual attributes of items, inspectors can quickly determine whether they meet the required standards without the need for specialized equipment or in-depth testing.

In contrast, other methods mentioned in the options have different focuses and processes. For instance, using tools to measure dimensions is a more quantitative approach that involves precision instruments to evaluate specific measurements rather than visual assessment. Applying a quality control inspection encompasses a broader range of practices and methodologies that may include visual inspection but also involves more structured procedures and documentation. Conducting chemical tests on materials refers to a laboratory method used to analyze the composition or properties of materials, which is distinctly different from the observational focus of visual inspection.