The solar radiation least absorbed by the layers of the atmosphere before reaching Earth is visible light.

Here's why:

* Visible light has wavelengths that are relatively long, and it's not easily absorbed by the major atmospheric gases like nitrogen and oxygen. This is why we can see the sun and why the sky appears blue.

* Ultraviolet (UV) radiation is absorbed by the ozone layer.

* Infrared radiation is absorbed by greenhouse gases like carbon dioxide, water vapor, and methane.

While some visible light is scattered and reflected by the atmosphere, a significant portion reaches the Earth's surface.