White is a color that is perceived when all visible wavelengths of light are reflected off of an object. When white light, which is made up of all the colors of the rainbow, hits an object, some of the wavelengths are absorbed by the object while others are reflected back to the viewer. The wavelengths that are reflected determine the color that is perceived.

The ability of an object to reflect light is determined by its surface properties, such as its texture, smoothness, and chemical composition. An object with a smooth, uniform surface will tend to reflect light more evenly, resulting in a brighter appearance. Conversely, an object with a rough, irregular surface will tend to scatter light in different directions, resulting in a duller appearance.

White objects are able to reflect a wide range of wavelengths, including all the colors of the rainbow, because they have a smooth, uniform surface that does not absorb any particular wavelengths of light. This is why white paper, for example, appears bright and vibrant when it is illuminated by white light.

In contrast, black objects absorb all wavelengths of light and do not reflect any back to the viewer. This is why black objects appear dark and absorbent under white light.

The ability of an object to reflect light is also influenced by its chemical composition. For example, certain chemicals and minerals, such as titanium dioxide and barium sulfate, have a high refractive index and are able to reflect a large portion of the light that hits them. These materials are often used in paints, coatings, and other products to create a bright, reflective finish.

In summary, white reflects light because it has a smooth, uniform surface that does not absorb any particular wavelengths of light. The chemical composition of an object can also play a role in its ability to reflect light, with certain chemicals and minerals being particularly effective at reflecting a wide range of wavelengths.