Reflection of Light

Study Notes

Light rays change direction when they reflect off a surface, move from one transparent medium into another, or travel through a medium whose composition is continuously changing.

States that, on reflection from a smooth surface, the angle of the reflected ray is equal to the angle of the incident ray.
Angles are measured with respect to the normal to the surface (a line perpendicular to the surface).
The reflected ray is always in the plane defined by the incident ray and the normal to the surface.

Plane and curved mirrors produce images that can be understood using the law of reflection.
Most natural surfaces are rough on the scale of the wavelength of light, causing parallel incident light rays to be reflected in many different directions (diffuse reflection).
Diffuse reflection allows us to see most illuminated surfaces from any position.

Occurs when light traveling in one transparent medium encounters a boundary with a second transparent medium (e.g., air and glass).
A portion of the light is reflected, and a portion is transmitted into the second medium.
As transmitted light moves into the second medium, it changes its direction of travel (refraction).
Law of Refraction (Snell's Law): n1 sin θ1 = n2 sin θ2, where n1 and n2 are the indices of refraction of the first and second media, respectively.

A dimensionless constant equal to the ratio of the speed of light in a vacuum to its speed in a medium.

Reflection: Light rebounds after hitting a surface (e.g., mirrors).
Refraction: Light shifts its path as it travels through a material, causing the light to bend (e.g., lenses).

Reflection: Occurs on a plane, with the light entering the medium returning to the same medium.
Refraction: Occurs when light passes through a surface, changing direction and medium.