Terms mirror is part of an imaginary sphere Centre of Curvature (C) – the centre of the sphere Vertex (V) – point where the C meets the centre of the mirror Principal Axis (P) – line between the C and V, forms a right angle with the mirror
Converging Mirrors (Concave) edges curve towards you eg. make-up/shaving mirrors all light rays parallel to principal axis converge (meet) at one point (focus) Focus (F) – is halfway between V and C principal axis centre of curvature vertex
A light ray parallel to the principal axis is reflected through the focus. This is how the focus is defined. A ray through F will reflect parallel to the principal axis. A ray aimed at the vertex will follow the law of reflection Drawing Ray Diagrams for Converging Mirrors an image forms when the rays come together at F if they do not converge (meet) there is no image there are 4 rules to locating objects in converging mirrors: A light ray through the centre of curvature is reflected back onto itself. Reflection From Curved Surfaces
Applications of Converging Mirrors show things up closely (makeup/shaving mirrors) Solar Cookers – focuses rays on one point in order to cook food Early Reflecting Telescopes – capture light from outer space to meet at F http://astro- canada.ca/_en/a2304.html http://astro- canada.ca/_en/a2304.html Hubble Telescope – in use today HubbleSite - Two Decades Unveiling the Universe HubbleSite - Two Decades Unveiling the Universe
2. Diverging (Convex) Mirrors edges are thicker than centre of mirror show a wide area (eg. store security mirrors) light rays diverge (spread apart) after they hit the mirror
Locating Images in Diverging Mirrors light rays always diverge after they strike a diverging mirror similar rules to converging mirrors C and F are located behind the mirror
Drawing Ray Diagrams for Diverging Mirrors 1.Draw the incident ray from the object to the mirror following one rules above. 2.Draw the reflected ray. 3.Extend the reflected ray beyond the mirror using a dotted line. 4.Repeat for another light ray. 5.Find the location of the image where the dotted lines cross.
SALT of Diverging Mirrors S – smaller A – upright L – behind mirror T – virtual *always same no matter of objects location to mirror Characteristics of Images Formed by Mirrors