When light encounters an obstacle such as a wall, it can be either absorbed, transmitted, reflected, or refracted. The way in which light is blocked depends on the characteristics of the obstacle and the properties of the light.
For example, a solid object such as a wall absorbs light, meaning that the energy of the light is transferred to the object, causing the object to heat up. This can result in the object becoming warmer, such as a wall or floor in direct sunlight, or it can result in the object changing its chemical properties, such as with photosensitive materials like photographic film.
Reflection occurs when light bounces off an object, changing the direction of the light. This can result in a mirror image or a diffuse reflection, depending on the characteristics of the object.
Refraction occurs when light passes through an object, changing the direction of the light. This can occur when light passes through transparent materials such as water or glass.
Finally, light can also be blocked by scattering, which occurs when light is dispersed in many different directions as it encounters small particles in the atmosphere, such as dust or water droplets. This is why the sky appears blue during the day, as the shorter blue wavelengths of light are scattered more than the longer wavelengths of red and orange light.