**Plane of Incidence**

The plane of incidence is a concept used in optics to describe the orientation of light rays incident on a surface. When light waves encounter a boundary between two different mediums, such as air and glass, they can be refracted or reflected depending on the angle at which they strike the surface. The plane of incidence refers to the plane that contains both the incident ray and the normal to the surface at the point of incidence.

**Explanation:**

When light waves travel from one medium to another, they change direction due to the change in speed. The angle at which the light wave strikes the boundary is known as the angle of incidence. The plane that contains the incident ray and the normal to the surface is called the plane of incidence.

1. **Incident Ray:** The incident ray is the path taken by the light wave as it approaches the boundary between two mediums.
2. **Angle of Incidence:** The angle of incidence is the angle between the incident ray and the normal to the surface at the point of incidence.
3. **Normal:** The normal is a line perpendicular to the surface at the point of incidence.
4. **Plane of Incidence:** The plane of incidence is the plane that contains both the incident ray and the normal to the surface at the point of incidence.

The plane of incidence is an important concept in optics because it helps determine the behavior of light waves at the boundary. When light waves strike a surface, they can be reflected, refracted, or absorbed. The angle of incidence and the properties of the mediums involved determine the nature of the interaction.

**Plane of Reflection**

The plane of reflection is another concept related to the behavior of light waves at a boundary. When light waves strike a reflective surface, such as a mirror, they bounce off in a predictable manner. The plane of reflection refers to the plane containing both the incident ray and the reflected ray.

**Explanation:**

1. **Reflected Ray:** The reflected ray is the path taken by the light wave as it bounces off the reflective surface.
2. **Angle of Reflection:** The angle of reflection is the angle between the reflected ray and the normal to the surface at the point of reflection.
3. **Plane of Reflection:** The plane of reflection is the plane that contains both the incident ray and the reflected ray.

The plane of reflection is important because it helps determine the direction and angle at which the light waves are reflected. According to the law of reflection, the angle of incidence is equal to the angle of reflection. The plane of reflection provides a visual representation of this relationship.

In summary, the plane of incidence and the plane of reflection are concepts used to describe the behavior of light waves at boundaries. The plane of incidence contains the incident ray and the normal to the surface, while the plane of reflection contains the incident ray and the reflected ray. Understanding these concepts is crucial in understanding the reflection and refraction of light.

Incidence of plane : the plane which contains the surface normal and the propagation vactor of the incoming radiation

plane of reflection : a plane through a crystal that divides the crystal into two halves of mirror images of each other