What happens to laser light when the diameter of an optic fiber decreases?

When the diameter of an optic fiber decreases, the power density of the laser light that is transmitted through that fiber increases. This is because power density is defined as the power per unit area. When the cross-sectional area of the fiber becomes smaller due to a decrease in diameter, the same amount of light power is concentrated over a smaller area. As a result, the intensity of the light increases, leading to a higher power density.

This increased power density can enhance the efficiency of light transmission in certain applications, such as when focusing laser light for medical procedures or industrial cutting. It's important to note that the other options do not accurately describe the effect of decreasing fiber diameter on laser light properties in the same way. For example, while a smaller diameter can potentially lead to issues like beam divergence depending on other factors, the direct result of reduced diameter is a rise in power density.