What is the effect of increasing the matrix size of an image?

Increasing the matrix size of an image effectively means that there are more pixels being used to represent the same area. As a result, the overall pixel size decreases since the same physical dimensions of the image are now divided into a greater number of smaller pixels. Smaller pixels enhance the spatial resolution because they can capture finer details in the image.

Spatial resolution is defined as the ability of an imaging system to distinguish small details in the image. When the pixel size decreases, the image can represent finer details more accurately, thus improving the spatial resolution. The combination of a smaller pixel size and greater spatial detail is why increasing the matrix size has such a significant positive impact on image quality.

Thus, both the decrease in pixel size and the increase in spatial resolution occur simultaneously when the matrix size is increased, making this the correct answer.