For Friday Finish chapter 23 Homework –Chapter 23, exercise 15.
Chapter 23
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Transcript of Chapter 23
Chapter 23Chapter 23Mirrors and LensesMirrors and Lenses
Types of Images for Types of Images for Mirrors and LensesMirrors and Lenses
A A real imagereal image is one in which is one in which light light actually passes throughactually passes through the image point the image point Real images can be displayed on screensReal images can be displayed on screens
A A virtualvirtual imageimage is one in which the is one in which the light light does not pass throughdoes not pass through the image point the image point The light appears to come (diverge) from The light appears to come (diverge) from
that pointthat point Virtual images cannot be displayed on Virtual images cannot be displayed on
screensscreens
More About ImagesMore About Images To find where an To find where an
image is formed, it image is formed, it is always is always necessary to follow necessary to follow at least two rays of at least two rays of light as they reflect light as they reflect from the mirror. from the mirror. The image formed The image formed by the flat mirror is by the flat mirror is a virtual imagea virtual image
Object distance Image distance
Flat MirrorFlat Mirror Simplest possible mirrorSimplest possible mirror Properties of the image Properties of the image
can be determined by can be determined by geometrygeometry
One ray starts at One ray starts at PP, , follows path follows path PQPQ and and reflects back on itselfreflects back on itself
A second ray follows A second ray follows path path PRPR and reflects and reflects according to the Law of according to the Law of ReflectionReflection
p=q!
Properties of the Image Properties of the Image Formed by a Flat MirrorFormed by a Flat Mirror The image is as far behind the mirror The image is as far behind the mirror
as the object is in frontas the object is in front pp = = qq
The image is unmagnified, The image is unmagnified, MM=1=1 The image is virtualThe image is virtual The image is uprightThe image is upright
It has the same orientation as the objectIt has the same orientation as the object There is an apparent left-right reversal There is an apparent left-right reversal
in the imagein the image
Application – Day and Application – Day and Night Settings on Car Night Settings on Car MirrorsMirrors
With the daytime setting, the bright beam of With the daytime setting, the bright beam of reflected light is directed into the driver’s eyesreflected light is directed into the driver’s eyes
With the nighttime setting, the dim beam (With the nighttime setting, the dim beam (DD) ) of reflected light is directed into the driver’s of reflected light is directed into the driver’s eyes, while the bright beam goes elsewhereeyes, while the bright beam goes elsewhere
23.2 Spherical Mirrors23.2 Spherical Mirrors A A spherical mirrorspherical mirror has the shape of a has the shape of a
segment of a spheresegment of a sphere A A concave concave spherical mirrorspherical mirror has the has the
silvered surface of the mirror on the silvered surface of the mirror on the inner, or concave, side of the curveinner, or concave, side of the curve
A A convexconvex spherical mirror spherical mirror has the has the silvered surface of the mirror on the silvered surface of the mirror on the outer, or convex, side of the curveouter, or convex, side of the curve
Concave Mirror, NotationConcave Mirror, Notation The mirror has a The mirror has a radius radius
of curvatureof curvature of of RR Its Its center of curvaturecenter of curvature
is the point is the point CC Point Point VV is the center of is the center of
the spherical segmentthe spherical segment A line drawn from A line drawn from CC to to
VV is called the is called the principle principle axisaxis of the mirror of the mirror
II is the image point is the image point
Focal LengthFocal Length If an object is very far If an object is very far
away, then away, then pp and 1/ and 1/pp 0; 0;
qq==RR/2/2 Incoming rays are Incoming rays are
essentially parallelessentially parallel In this special case, the In this special case, the
image point is called the image point is called the focal pointfocal point
The distance from the The distance from the mirror to the focal point is mirror to the focal point is called the called the focal lengthfocal length The focal length is ½ the The focal length is ½ the
radius of curvature radius of curvature f = R/2
Focal Length Shown by Focal Length Shown by Parallel RaysParallel Rays
23.3 Convex Mirrors23.3 Convex Mirrors A A convexconvex mirror is sometimes called a mirror is sometimes called a
divergingdiverging mirrormirror The rays from any point on the object diverge The rays from any point on the object diverge
after reflection as though they were coming after reflection as though they were coming from some point behind the mirror from some point behind the mirror
The image is virtual because it lies behind The image is virtual because it lies behind the mirrorthe mirror at the point where the reflected at the point where the reflected rays appear to originaterays appear to originate
In general, the image formed by a convex In general, the image formed by a convex mirror is mirror is upright, virtual, and smaller than the upright, virtual, and smaller than the objectobject
Image Formed by a Image Formed by a Convex MirrorConvex Mirror
Ray DiagramsRay Diagrams A A ray diagramray diagram can be used to can be used to
determine the position and size of an determine the position and size of an imageimage
They are graphical constructions which They are graphical constructions which tell the overall nature of the imagetell the overall nature of the image
They can also be used to check the They can also be used to check the parameters calculated from the mirror parameters calculated from the mirror and magnification equationsand magnification equations
Drawing A Ray DiagramDrawing A Ray Diagram To make the ray diagram, you need to knowTo make the ray diagram, you need to know
The position of the objectThe position of the object The position of the center of curvatureThe position of the center of curvature
Three rays are drawnThree rays are drawn They all start from the same position on the They all start from the same position on the
objectobject The intersection of any two of the rays at a The intersection of any two of the rays at a
point locates the imagepoint locates the image The third ray serves as a check of the The third ray serves as a check of the
constructionconstruction
The Rays in a Ray The Rays in a Ray DiagramDiagram
Ray 1 is drawn parallel Ray 1 is drawn parallel to the principle axis to the principle axis and is reflected back and is reflected back through the focal point, through the focal point, FF
Ray 2 is drawn through Ray 2 is drawn through the focal point and is the focal point and is reflected parallel to the reflected parallel to the principle axisprinciple axis
Ray 3 is drawn through Ray 3 is drawn through the center of curvature the center of curvature and is reflected back on and is reflected back on itselfitself
1
3
2
Notes About the RaysNotes About the Rays The rays actually go in all directions The rays actually go in all directions
from the objectfrom the object The three rays were chosen for their The three rays were chosen for their
ease of constructionease of construction The image point obtained by the ray The image point obtained by the ray
diagram must agree with the value diagram must agree with the value of of qq calculated from the mirror calculated from the mirror equationequation
Ray Diagram for Concave Ray Diagram for Concave Mirror, Mirror, pp > > RR
The image is realThe image is real The image is invertedThe image is inverted The image is smaller than the objectThe image is smaller than the object
Ray Diagram for a Ray Diagram for a Concave Mirror, Concave Mirror, pp < < ff
The image is virtualThe image is virtual The image is uprightThe image is upright The image is larger than the objectThe image is larger than the object
Ray Diagram for a Convex Ray Diagram for a Convex MirrorMirror
The image is virtualThe image is virtual The image is uprightThe image is upright The image is smaller than the objectThe image is smaller than the object
Notes on ImagesNotes on Images With a concave mirror, the image may be either With a concave mirror, the image may be either
real or virtualreal or virtual When the object is outside the focal point, the image is When the object is outside the focal point, the image is
realreal When the object is at the focal point, the image is When the object is at the focal point, the image is
infinitely far away (to the left in the previous diagrams)infinitely far away (to the left in the previous diagrams) When the object is between the mirror and the focal When the object is between the mirror and the focal
point, the image is virtualpoint, the image is virtual With a convex mirror, the image is always virtual With a convex mirror, the image is always virtual
and uprightand upright As the object distance increases, the virtual image gets As the object distance increases, the virtual image gets
smallersmaller