Milady Electricity Practice Test 2025 - Free Practice Questions and Study Guide

The ozone layer primarily serves as a protective barrier in the Earth's atmosphere that absorbs the majority of the sun's harmful ultraviolet (UV) radiation. The correct choice indicates UVC radiation, which is the most harmful type of UV radiation.

UVC rays have shorter wavelengths and are the most energetic among the UV spectrum. They are mostly absorbed by the ozone layer and do not reach the Earth's surface in significant amounts. The presence of the ozone layer is crucial for shielding living organisms from the potentially damaging effects of UVC radiation, which can lead to DNA damage and other harmful effects.

In contrast, UVA radiation, which has longer wavelengths than UVC, is not adequately blocked by the ozone layer and can penetrate the skin, contributing to skin aging and the risk of skin cancer. UVB radiation, while also partially absorbed by the ozone layer, does reach the surface and can lead to skin damage, sunburn, and increased skin cancer risk. Visible light isn't harmful in the same way UV radiation is and isn't blocked by the ozone layer. Therefore, the choice correctly identifies UVC as the type of UV radiation that is effectively blocked by the ozone layer.