8. THE LAWS OF REFLECTION FIRST LAWS The incident ray, the reflected ray and the nornal all lie in the same plane SECOND LAWS The angle of incidence, I is equal to the angle of reflection, r
9. THE LAWS OF REFLECTION When a ray of light strikes a plane mirror, the light ray reflects off the mirror. Reflection involves a change in direction of the light ray. The convention used to express the direction of a light ray is to indicate the angle which the light ray makes with a normal drawn to the surface of the mirror. The angle of incidence is the angle between this normal and the incident ray; the angle of reflection is the angle between this normal and the reflected ray. According to the law of reflection, the angle of incidence equals the angle of reflection. These concepts are illustrated in the animation at the right.
10. Image Formation for Plane Mirrors In the animation above, an object is positioned in front of a plane mirror. The plane mirror will produce an image of the object on the opposite side of the mirror. The distance from the onject to the mirror equal the distance from the image to the mirror. Any person viewing this image must sight at this image position.
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13. The image of an object in a plane mirror (a) Same size as object (b) Laterally inverted (c) virtual (d) As far behind the mirror
17. Ray diagrams of convex and concave mirror T wo rules of reflection for concave mirrors. They are: Any incident ray traveling parallel to the principal axis on the way to a concave mirror will pass through the focal point upon reflection. Any incident ray passing through the focal point on the way to a concave mirror will travel parallel to the principal axis upon reflection. The revised rules can be stated as follows: Any incident ray traveling parallel to the principal axis on the way to a convex mirror will reflect in 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 .
18. principal axis Concave mirror P C F Convex mirror Any incident ray traveling parallel to the principal axis on the way to a concave mirror will pass through the focal point upon reflection. Any incident ray traveling parallel to the principal axis on the way to a convex mirror will reflect in a manner that its extension will pass through the focal point . P C F
19. P C F 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 . P C F Any incident ray passing through the focal point on the way to a concave mirror will travel parallel to the principal axis upon reflection. Concave mirror Convex mirror
20. P C F A line through the centre of curvature, C from the top of the object Concave mirror Convex mirror P C F A line through the centre of curvature, C from the top of the object
