Final answer:
The angle of reflection is equal to the angle of incidence, so if light hits a diamond surface at a 30.0° angle, it is reflected at a 30.0° angle relative to the normal.
Step-by-step explanation:
When light is incident on the surface of a diamond at a particular angle, known as the angle of incidence, it is not only refracted but also reflected.
According to the law of reflection, the angle of reflection is equal to the angle of incidence. This means that if light rays are incident at a 30.0° angle, the light rays will also be reflected at a 30.0° angle relative to the normal. This is consistent regardless of the medium (in this case, diamond).
The index of refraction of diamond is higher than that of water, which implies that light will bend more upon entering the diamond and thus the angle of refraction will be smaller compared to its refraction in water. Moreover, total internal reflection plays a significant role in diamonds as their critical angle is only 24.4°. When light enters a diamond, most of it will be internally reflected, contributing to the diamond's sparkle.