Reflection and Mirrors

• A mirror is not necessarily a silvered plate of glass. Rather, it is any surface that is smooth enough to produce a regular reflection of light incident upon it.
• There are two types of mirrors: plane mirrors and spherical mirrors.
• plane mirror is one with a flat surface. The ordinary mirror you have at home where you see the exact image of yourself is a plane mirror
• Plane mirrors are also used by architects or interior designers to make a room appear bigger
• spherical mirror has a reflecting surface taken from the surface of a sphere. It may be concave or convex.
• concave mirror curves inward in the direction of the incident rays
• convex mirror bulges outward to the incident rays.
• The hollow part of a shiny spoon is a concave mirror. But if you turn it over, it becomes a convex mirror.
• shiny Christmas ball, the rearview mirrors of cars, and the dome mirrors in supermarkets are convex mirrors
• Shaving mirrors, makeup mirrors, and dentist's mirrors are concave mirrors.
• the real image is formed by the actual intersection of reflected rays. It is formed in front of the mirror and is always upside down relative to the object.
• A virtual image is formed behind the mirror and is upright relative to the object. There is no actual intersection of reflected rays. But if you extend the rays as if they came from behind the mirror, there is an intersection
• The image distance is equal to the object distance. That is, di = do
• Plane mirror images are virtual, upright, and of the same size as the object, and laterally reversed.
• center of curvature C is the center of the sphere from where the mirror was taken.
• vertex V is the center of the mirror. It is sometimes called the pole of the mirror.
• radius of curvature R is the radius of the sphere. It is the distance between C and V.
• principal axis or optical axis is a straight line joining C and V.
• aperture AB refers to the width of the mirror.
• principal focus F is the point where the reflected rays meet as in the case of a converging mirror (concave mirror), or the point where the reflected rays seem to come from behind a diverging mirror (convex mirror).
• The focal length f is the distance from the vertex to the principal focus
• When parallel rays strike a concave mirror, the rays will be reflected and meet at a single point called the principal focus
• Since there is an actual meeting of reflected rays in concave mirrors, the principal focus is real
• the principal focus of a convex mirror is virtual
• Reflection: bouncing back of light in the same medium it has been striking
• Incident Ray: ray that strikes a surface
• Reflected Ray: ray that rebounds a rebounds from the surface
• Angle of incidence 0: angle between incident and normal
• Normal: line that is perpendicular to the surface at the point of incidence
• Angle of reflection: angle between reflected and normal
• Regular or specular: reflection form a smooth surace
• Diffuse: reflection from rough surfaces
• The incident ray, normal, and reflected ray all lie in one plane
• when a group of parallel rays strikes a surface, the reflected are parallel to each other
• when a group of parallel rays strikes a rough surface, individual rays are reflected from a surface so they scatter in different directions and cannot be parallel