What is the role of the sensor in a camera?

The role of the sensor in a camera is crucial, as it is responsible for converting the light that passes through the lens into an electrical signal. This process involves capturing the incoming photons and translating their intensity and color information into a digital format that can be processed, stored, and displayed. The sensor essentially acts as the heart of digital imaging, transforming visual scenes into data that can be manipulated and shared.

Focusing light onto the image is primarily the responsibility of the lens, which directs the light appropriately onto the sensor. While adjusting the aperture size is also a function related to the lens and its mechanics, it doesn't describe the sensor's direct role. As for measuring dust and moisture resistance, this relates more to the camera's overall design and construction rather than the function of the sensor specifically. Thus, the option highlighting the sensor's role in converting light to a digital signal accurately encapsulates its key function in the camera system.