Reflection

Laws of Reflection

The laws of reflection describe how light (or any other wave) behaves when it encounters a reflective surface, such as a mirror.

The First Law of Reflection

The incident ray, the reflected ray, and the normal to the surface at the point of incidence all lie in the same plane.

This means that the path taken by the light ray before and after reflection, as well as the normal, all lie in a single two-dimensional plane. This plane is typically visualized as a flat surface that extends through the point of incidence on the reflective surface.

The Second Law of Reflection

The angle of incidence equals the angle of reflection

Mathematically, $\theta_i = \theta_r$

Reflected Image

Images formed in a plane mirror has the following characteristics:

1. The image formed is the same size as the object.
2. The image formed is laterally inverted (“left-right opposite”).
3. The image formed is upright (not slanted at any angle, and not upside down compared to the object).
4. The image formed is virtual.
5. The (perpendicular) distance of the image from the (surface of the plane) mirror is equal to the (perpendicular) distance of the object from the (surface of the plane) mirror.

Using the simulation below, adjust the positions of the object and eye to observe how the ray of light reaches the eye from the object. You can also adjust the length and position of the mirror. At certain positions, the image will no longer be visible to the eye as the ray of light will not reflect off the mirror in a direction that leads to the eye.

Drawing a Ray Diagram of a Plane Mirror

Experiment to Verify Laws of Reflection