# Curved Mirrors Curved mirrors are like plane mirrors

• Slides: 22

Curved Mirrors • Curved mirrors are like plane mirrors • they too have smooth, shiny surfaces that reflect light. • The surface can either curve in (concave) or out (convex) as shown below

Concave mirrors v. They curve inwards v. They can form two types of image v. If the light rays come from something close, the image is upright and magnified v. It is a virtual image

If the light rays come from something distant, they come to a focus after reflection Converging mirror They converge (come together) to form a small inverted image which can be picked up on a screen The type of image is called a real image The rays of light actually meet to form it.

ØRays from very distant things are nearly parallel to each other Ø a concave mirror brings parallel rays to a focus at a point called the principal focus (F) Ø the distance from the mirror to the principal focus is called the focal length Ø highly curved mirror have short focal lengths

Remember, the concave mirror is part of a sphere The centre of curvature of a mirror is the centre of the sphere part of whose surface forms the curved mirror It is labelled C

V The principal axis of the mirror is the line going through the centre of curvature and the centre of the mirror

The point on the mirror's surface where the principal axis meets the mirror is known as the vertex and is denoted by the letter V in the diagram. The distance from the vertex to the center of curvature is known as the radius of curvature (represented by R). The radius of curvature is the radius of the sphere from which the mirror was cut. Since the focal point is the midpoint of the line segment adjoining the vertex and the center of curvature, the focal length would be one-half the radius of curvature.

How to locate the image in Converging (Concave) Mirror To determine the image of an object in front of a concave mirror, v you need to draw at least two incident rays from the top of the object v these rays will be reflected off the mirror and may not cross to form an image

C F V Principal axis

C F V

Drawing an image on Concave mirror Using three kinds of rays 1. The ray parallel to principle axis is reflected through the focal point (F) 2. The ray passing through F is reflected parallel to the principle axis 3. The ray passing through the center of curvature C is reflected along its same path through C

Three kinds of rays C F V

Forming an image (Object beyond C) C Inverted, virtual, smaller F V Principal axis

Object between C and F C Inverted, real, larger F V Principal axis

Object inside F or between F and V Principal axis C Upright, virtual, bigger F V

Object at C C inverted, real, same size F V Principal axis

Convex Mirror Characteristic of convex mirror 1. A convex mirror is part of the outer surface of a hollow sphere 2. A convex mirror produces diverged rays 3. A convex mirror does not form real images 4. Convex mirror in daily life, used in cars, and used in stores to observe shoppers.

Principal axis

V Principlal axis F C

Three kinds of light rays V F C Principal axis

Forming an image in a convex mirror Principal axis

Forming an image in convex mirror Three kinds of rays 1. The ray parallel to the principal axis is reflected as if it is from focal point (f) 2. The ray to focal point is reflected parallel to the principal axis 3. The ray to the center of curvature C is reflected along its same path through C