Second Law of Reflection
States that the incident ray, the reflected ray, and the normal to the surface at the point of incidence all lie in the same plane.
What is Second Law of Reflection?
The ray of light falling on the reflecting surface.
Key points
- Define the Second Law of Reflection.
- Identify the incident ray, reflected ray, and normal in a reflection diagram.
- Explain the concept of the "plane of incidence."
- Apply the law to correctly draw ray diagrams for reflection.
Common exam trap
Assuming the reflected ray can deviate out of the plane formed by the incident ray and the normal.
Definitions
- Term
Incident Ray
- Meaning
The ray of light falling on the reflecting surface.
- Term
Reflected Ray
- Meaning
The ray of light bouncing back from the reflecting surface.
- Term
Normal
- Meaning
An imaginary line drawn perpendicular to the reflecting surface at the point of incidence.
- Term
Point of Incidence
- Meaning
The point where the incident ray strikes the reflecting surface.
- Term
Plane of Incidence
- Meaning
The plane containing the incident ray, the reflected ray, and the normal.
Learning objectives
Define the Second Law of Reflection.
Identify the incident ray, reflected ray, and normal in a reflection diagram.
Explain the concept of the "plane of incidence."
Apply the law to correctly draw ray diagrams for reflection.
Prerequisites
Basic understanding of light as a ray.
Concept of a normal to a surface.
Familiarity with 2D and 3D geometry.
Common mistakes
Assuming the reflected ray can deviate out of the plane formed by the incident ray and the normal.
Incorrectly drawing the normal not perpendicular to the surface.
Confusing the plane of incidence with the plane of the mirror itself (for curved mirrors, they are different).
Keywords
Reflection
Laws of Reflection
Incident Ray
Reflected Ray
Normal
Plane of Incidence
Coplanar
Ray Optics
Practice preview
According to the second law of reflection, the incident ray, the reflected ray, and the normal to the surface at the point of incidence all lie in the:…
easy
Which of the following statements correctly describes the second law of reflection?…
easy
Consider a light ray incident on a plane mirror. Which statement about the incident ray, reflected ray, and the normal at the point of incidence is always true according to the laws of reflection?…
medium