17.2 Curved Mirrors

Waseem A. Alhausani M.Sc.

ATHS – RAK

8/2/2012

Objectives

Define the concave and convex mirror and distinguish between them.

Describe images formed by curved mirrors: location, orientation and size.

Use the mirror equation to determine the image position and height, the focal length and magnification of the curved mirrors

Concave Mirror

The center C of a concave mirror is outside the mirror.

Focal point F is also outside the mirror, half way between the center and the surface of the mirror.

The focal length f is half of the radius.

Significance of the focal point

All light rays that are parallel to the axis will pass (after extrapolating for convex mirror) through the focal point!

For a concave mirror, the light can pass through the focal point.

Image from a concave mirror: Image from a concave mirror: case 1case 1

Step 1 Step 2

Step 3 Step 4

Image from a concave mirror: case 1case 1

Properties of the Image

If we put an object outside of the center of a concave mirror, we find the image isReal, in the sense that all light rays pass

through the image. Inverted, in the sense that the direction of the

arrow has been changed.The image is smaller!

Animation for case 1

Image for a concave mirror: case 2

If the object is in between the center and the focal point, the image is Real InvertedMagnified in the sense that the image is

bigger than the real object.

The direction of the light rays can be reversed and the result is still physically possible! (or the image and object interchanged)

Animation for case 2

Image from a concave mirror: Image from a concave mirror: case 3case 3

Image from a concave mirror: case 3case 3

Animation for case 3

Properties of the image

If the object is closer to the mirror than the focal point F, the image isVirtual, it is behind the mirrorUpright, not invertedMagnified

Can be used for shaving!

SummarySummary

Question

Some of the really-cool Some of the really-cool applicationsapplications

Suppose you put a point source of light at F. All rays will be reflected back parallel to the axis of mirror: a neat way to construct a parallel beam!Applications: flashlight! Headlight in the car.

Conversely, if one has parallel rays, all are reflected to pass through F. So all light energy is focused to one point!

Mathematical Method of locating the Image

Convex MirrorsCurves outward

Convex MirrorsReduces imagesVirtual images

Use: Rear view mirrors, store security…

Question

Assessment

http://www.glencoe.com/qe/scienceOLC.php?qi=7921

H.W: Problems 22-26 / page: 473.

Quiz (Next week / to be appointed… )