CURVED MIRRORS

F = principal focus C = centre of curvature V = vertex F • C • V • Principal axis Principal axis

F • C •

Rules for drawing ray diagrams for concave mirrors 1. Any incident ray travelling parallel to the principal axis will reflect on the concave mirror and pass through the focal point.

C • F • V •

Rules for drawing ray diagrams for concave mirrors 2. Any incident ray that passes through F will reflect and travel parallel to the principal axis.

C • F •

Rules for drawing ray diagrams for concave mirrors 3. Any incident ray that passes through C will reflect and travel through C again.

C • F • V •

Rules for drawing ray diagrams for concave mirrors Memorize the three rules!!!!! 1) 2) 3) This is a must!!!

Prediction for Image Created by an Object Past the Point of Curvature…kind of far away • F • Location: Orientation: Size: Type:

Prediction for Image Created by an Object Past the Point of Curvature…even further away • F • Location: Orientation: Size: Type:

Prediction for Image Created by an Object Between the Focal Point and the Centre of Curvature….kind of close C • F • Location: Orientation: Size: Type:

Prediction for Image Created by an Object At the Centre of Curvature • F • Location: Orientation: Size: Type:

Prediction for Image Created by an Object At the Focal Point • F • Location: Orientation: Size: Type:

Prediction for Image Created by an Object in Front of the Focal Point… Prediction for Image Created by an Object in Front of the Focal Point….very near the mirror C • F • Location: Orientation: Size: Type:

Summary LOST characteristics of Images formed with a Concave Miror 1) Very Far…. 2) Getting Near… 3) At C… 4) At F… 5) Very near … Know this too!

Rules for drawing ray diagrams for convex mirrors 1.Any incident ray travelling towards a convex mirror such that its extension passes through the focal point will reflect and travel parallel to the principal axis

2.Any incident ray travelling parallel to the principal axis on the way to a convex mirror will reflect in a way that its extension will pass through the focal point. 3.Any incident ray travelling towards a convex mirror such that its extension passes through the centre of curvature will reflect and travel along the same path.

Any two of these rules can be used to construct ray diagrams. A ray diagram is a tool used to determine the location, size, orientation, and type of image formed by a mirror. A similar method for constructing ray diagrams for concave mirrors is used for convex mirrors.

The method of drawing ray diagrams for convex mirrors is described below. From the top of the object , draw two incident rays travelling towards the mirror. Using a straight edge, draw one ray so that it travels towards the focal point on the opposite side of the mirror. It will strike the mirror before reaching the focal point

Draw the second ray such that it travels exactly parallel to the principal axis. Place arrowheads upon the rays to indicate their direction of travel. The ray that travels towards the focal point will reflect and travel parallel to the principal axis. The ray which travelled parallel to the principal axis on the way to the mirror will reflect and travel in a direction such that its extension passes through the focal point.

. Align a straight edge with the point of incidence and the focal point, and draw the second reflected ray. Place arrowheads to indicate their direction of travel. The two rays should be diverging upon reflection. Locate and mark the image of the top of the object where the two reflected rays intersect. Since the two reflected rays are diverging, they must be extended behind the mirror in order to intersect

F • C • Image characteristics: smaller upright virtual Behind the mirror

F • C •

Will these always be the characteristics of an image produced by a convex mirror? Can convex mirrors ever produce real images? Inverted images? Magnified Images? Look at these three different ray diagrams for objects positioned at different locations along the principal axis.

The diagrams above shows that in each case, the image is located behind the convex mirror a virtual image an upright image reduced in size (i.e., smaller than the object)

Unlike concave mirrors, convex mirrors always produce images which share these characteristics. The location of the object does not effect the characteristics of the image. Location: inside mirror Orientation: upright Size: small Type: virtual

Another characteristic of the images of objects formed by convex mirrors pertains to how a change in object distance effects the image distance and size. As the object distance is decreased, the image distance is decreased and the image size is increased.