Why is the incidence ray brighter than the ray a?

The incidence ray is often brighter than ray A due to the difference in intensity and energy distribution as the light interacts with surfaces or media. When the incident light strikes a surface, some of its energy is reflected, while some may be absorbed or transmitted, depending on the material's properties. If ray A represents a refracted or reflected ray that has lost some energy due to these interactions, it will appear dimmer compared to the incidence ray. Additionally, factors like the angle of incidence and the nature of the surface can further influence the brightness of the rays.