First Law of Reflection
States that the angle of incidence is always equal to the angle of reflection.
What is First Law of Reflection?
The ray of light that strikes a surface.
Key points
- Understand the spatial relationship between incident ray, reflected ray, and normal.
- Identify the plane in which reflection occurs.
- Apply the law to simple reflection scenarios.
Common exam trap
Confusing the plane of incidence with the plane of reflection.
Definitions
- Term
Incident Ray
- Meaning
The ray of light that strikes a surface.
- Term
Reflected Ray
- Meaning
The ray of light that bounces off a surface.
- Term
Normal
- Meaning
A line perpendicular to the reflecting surface at the point of incidence.
- Term
Plane of Incidence
- Meaning
The plane containing the incident ray and the normal.
Learning objectives
Understand the spatial relationship between incident ray, reflected ray, and normal.
Identify the plane in which reflection occurs.
Apply the law to simple reflection scenarios.
Prerequisites
Basic understanding of light as a ray.
Concept of a surface and perpendicular lines (normal).
Common mistakes
Confusing the plane of incidence with the plane of reflection.
Assuming the incident ray, reflected ray, and surface are in the same plane (instead of the normal).
Keywords
Reflection
Incident Ray
Reflected Ray
Normal
Plane
Coplanar
Optics
Practice preview
According to the first law of reflection, the angle of incidence is:…
easy
A light ray is incident on a plane mirror such that the angle between the incident ray and the mirror surface is 30 degrees. What is the angle of reflection?…
hard
Which of the following statements correctly describes the first law of reflection?…
easy