MIRRORS AND REFLECTION

ReflectionThe change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated.

Law of reflectionWhen a ray of light reflects off a surface, the angle of incidence is equal to the angle of reflection.

Note: The angle of incidence, i, and the angle of reflection, r, are both measured from the normal line N.

Specular vs Diffuse ReflectionReflection off of smooth surfaces such as mirrors or a calm body of water leads to a type of reflection known as specular reflection. Reflection off of rough surfaces such as clothing, paper, and the asphalt roadway leads to a type of reflection known as diffuse reflection.

Virtual vs Real ImagesVirtual images are images that are formed in locations where light does not actually reach.

Real image is an image formed when light rays converge and pass through the image.

Image formed by plane mirrors

1. Virtual2. Upright3. left-right reversed4. the same distance from the mirror as the object's distance5. same size as the object.

Spherical mirrorsConcave mirrors were silvered on the inside of the sphere. Convex mirrors were silvered on the outside of the sphere.

Anatomy of a spherical mirror

R – radius of curvature A - VERTEXC – center of curvature f – focal F – focal point f = ½ R

Two rules of reflection for concave mirrors• Any incident ray traveling parallel to the principal axis on

the way to the mirror will pass through the focal point upon reflection.

• Any incident ray passing through the focal point on the way to the mirror will travel parallel to the principal axis upon reflection.

Two rules of reflection for convex mirrors• Any incident ray traveling parallel to the principal axis on

the way to a convex mirror will reflect in such a manner that its extension will pass through the focal point.

• Any incident ray traveling towards a convex mirror such that its extension passes through the focal point will reflect and travel parallel to the principal axis.

ApplicationWhy is the word “AMBULANCE” written in reversed in ambulances such as shown below?