The shape of an object can affect how it interacts with light in several ways.
First, the shape of an object can determine how light is reflected off of its surface. A smooth, curved surface will reflect light in a more diffuse manner, producing a soft, even reflection. A rough, uneven surface will scatter light in many different directions, producing a more irregular reflection.
Second, the shape of an object can also affect how light is absorbed by the object. An object with a highly absorbent surface will absorb more light than an object with a less absorbent surface. This is why black objects tend to absorb more light and heat than white objects, which tend to reflect more light.
Finally, the shape of an object can affect how light passes through it. An object with a transparent or translucent surface will allow light to pass through it, while an object with an opaque surface will block the passage of light. The shape of the object can also affect how light is refracted, or bent, as it passes through the object. An object with a curved surface, such as a lens, will refract light in a specific manner, while a flat surface will not.