Chapter 23

Section Objectives 23.1 Compare plane mirrors, concave mirrors, and convex mirrors. Describe the images formed by concave and convex

Mirrors 3 types of mirrors Plane Mirrors Concave mirrors Flat Concave mirrors Indent Convex mirrors Outdent

Plane Mirror Plane Mirrors have a flat surface. Light reflects off a mirror because it can not pass through the surface. The reflection of an object in a plane mirror is right side up and the same size as the object, but reversed left to right. Plane mirrors form virtual images. A virtual image is an image through which light does not travel

Ray Diagrams We use ray diagrams to show how light changes as it strikes mirrors or passes through lenses Light rays Going in? Green! Reflecting out? Red!

Plane Mirror Ray Diagrams First, we draw an image of the object on the other side of the mirror Distance A is equal to distance B and the image size is the same size as the object size. Intersections will give you the image location! Draw any small object you’d like under the left side “object” arrow

Intersections will give you the image location! Plane Mirror Ray Diagrams Second, we draw light rays from the image to the eye The image is virtual. Broken lines from the image to mirror indicate virtual rays. Virtual image: Light rays do not actually meet at the image position. Because of that, a virtual image cannot be projected on a screen. Continuous lines from the mirror to eye indicate the reflected rays. Intersections will give you the image location!

Intersections will give you the image location! Plane Mirror Ray Diagrams Third, we join the light rays from the mirror to the object Lines joining the object to the positions of the reflected rays on the mirror represent the incident rays by following the law of reflection. Intersections will give you the image location!

L.O.S.T. Mirror Images How can I easily describe the image formed?

L.O.S.T L- Location: location of the image (in front or behind the mirror). O- Orientation: which way the image is oriented compared to the original object (upright or inverted). S- Size: compared to original object is it same size, smaller or bigger? T- Type: is the image a real image or virtual image?

Section 19.1--Mirrors Let’s try! L: O: S: T: L: O: S: T:

Section 19.1--Mirrors Let’s try! L: O: S: T: L: O: S: T:

Plane Mirrors PROCESS BOX How does the LOST description compare for both of the images produced by plane mirrors?

Plane Mirrors Characteristics of a plane mirror image: L:Object distance from mirror = image distance from mirror O: Orientation is ALWAYS upright S: Object size = Image Size T: ALWAYS forms a virtual image Image is reversed- left to right

Concave Mirrors A concave mirror is curved inward. They can produce both a virtual or a real image. The point at which all light rays meet is called the focal point. Examples: automobile headlights, flashlights, Make-up mirrors

How Images Are Formed in Concave Mirrors

Concave Mirrors When does it make a real image? Object has to be farther away (behind) from the focal point When does it make a virtual image? Object has to be closer to (in front of) the focal point

Intersection will give you the image location! Concave Mirror Ray Diagrams Pick a point on the top of the object and draw two incident rays traveling towards the mirror. Using a straight edge, accurately draw one ray so that it passes exactly through the focal point on the way to the mirror. 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. Intersection will give you the image location!

Intersection will give you the image location! Concave Mirror Ray Diagrams Once these incident rays strike the mirror, reflect them according to the two rules of reflection for concave mirrors. The ray that passes through the focal point on the way to the mirror will reflect and travel parallel to the principal axis. Use a straight edge to accurately draw its path. The ray that traveled parallel to the principal axis on the way to the mirror will reflect and travel through the focal point. Place arrowheads upon the rays to indicate their direction of travel. Extend the rays past their point of intersection. Intersection will give you the image location!

Intersection will give you the image location! Concave Mirror Ray Diagrams Find the location of the bottom of the object If the bottom of the object lies upon the principal axis (as it does in this example), then the image of this point will also lie upon the principal axis and be the same distance from the mirror as the image of the top of the object. At this point the entire image can be filled in. Intersection will give you the image location!

Concave Mirrors What image was formed? L: O: S: T: Let’s try! L: O: S:

Concave Mirrors L: O: S: T: L: O: S: T:

Concave Mirrors PROCESS BOX How does the LOST description compare for both of the images produced by concave mirrors?

Smaller or same size as object Concave Mirror Characteristics of a Concave mirror image: Location of Object Location of Image Orientation of Image Size of Image Type of Image Past F In front of mirror Inverted Smaller or same size as object Real Between mirror and F Behind mirror Upright Larger than object Virtual

Convex Mirror A convex mirror curves outward. The object is virtual and appears smaller and upright. Convex mirrors spread out light; allowing the mirror to show a wide angle of view. Examples: Used in store aisles, hazardous traffic intersections, side mirrors on cars and buses.

Intersection will give you the image location! Convex Mirror Ray Diagrams Pick a point on the top of the object and draw two incident rays traveling towards the mirror. Using a straight edge, accurately draw one ray so that it travels towards the focal point on the opposite side of the mirror; this ray will strike the mirror before reaching the focal point; stop the ray at the point of incidence with the mirror. 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. Intersection will give you the image location!

Intersection will give you the image location! Convex Mirror Ray Diagrams 2. Once these incident rays strike the mirror, reflect them according to the two rules of reflection for convex mirrors. The ray that travels towards the focal point will reflect and travel parallel to the principal axis. The ray that traveled parallel to the principal axis on the way to the mirror will reflect and travel in a direction such that its extension on the other side of the mirror 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 upon the rays. Intersection will give you the image location!

Intersection will give you the image location! Convex Mirror Ray Diagrams Locate and mark the image of the top of the object. The image point of the top of the object is the point where the two reflected rays intersect. Since the two reflected rays are diverging, they must be extended behind the mirror in order to intersect. Using a straight edge, extend each of the rays using dashed lines. Draw the extensions until they intersect. The point of intersection is the image point of the top of the object. Both reflected rays would appear to diverge from this point. Intersection will give you the image location!

Intersection will give you the image location! Convex Mirror Ray Diagrams Find the location of the bottom of the object If the bottom of the object lies upon the principal axis (as it does in this example), then the image of this point will also lie upon the principal axis and be the same distance from the mirror as the image of the top of the object. At this point the complete image can be filled in. Intersection will give you the image location!

Convex Mirror L: O: S: T: L: O: S: T:

Convex Mirror Let’s try! L: O: S: T: PROCESS BOX How does the LOST description compare for both of the images produced by convex mirrors

Convex Mirror Characteristics of a convex mirror image: L: Image is ALWAYS behind mirror O: Orientation is ALWAYS upright S: Object size > Image Size T: ALWAYS forms a virtual image

Mirrors – reflect light Types of Mirrors Images Formed Virtual or Real Direction of Image Plane / Flat Virtual Upright/opposite Convex (Curves outward) Upright/smaller Concave (curves inward) Object – Focal- Mirror Real Upside down Focal- Object- Mirror Upright

Lenses Lens – an object made of transparent material that has one or two curved surfaces that can refract or bend light. The curvature and thickness of a lens affect the way it refracts light.

concave lens = divergent lens A concave lens is curved inward at the center (thinnest) and the thickest part at the outside edges. The light rays are spread out. Forms a small, upright virtual image. Concave lenses cure nearsightedness when an eyeball is too long Examples: a peep hole in a door, found in viewfinders of cameras, eyeglasses, telescopes. concave lens = divergent lens

Intersection will give you the image location! Concave lens Concave Lens Diagrams Pick a point on the top of the object and draw two incident rays traveling towards the lens. Draw one ray so that it travels towards the focal point on the opposite side of the lens; stop the ray at the point of incidence with the lens. Draw the second ray such that it travels exactly parallel to the center line. Add arrowheads Intersection will give you the image location!

Intersection will give you the image location! Concave Lens Concave Lens Diagrams Once these incident rays strike the lens, refract them according to the rules of refraction The ray that travels towards the focal point will refract through the lens and travel parallel to the center line. The ray that traveled parallel to the principal axis on the way to the lens will refract and travel in a direction such that its extension passes through the focal point on the object's side of the lens. Place arrowheads upon the rays to indicate their direction. Intersection will give you the image location!

Intersection will give you the image location! Concave Lens Concave Lens Diagrams Locate and mark the image of the top of the object. Since the refracted rays are diverging, they must be extended behind the lens in order to intersect. Using a straight edge, extend each of the rays using dashed lines. Draw the extensions until they intersect. The point of intersection is the image point of the top of the object. Draw the image in Intersection will give you the image location!

Intersection will give you the image location! Concave Lens Concave Lens Diagrams Draw in the image If the bottom of the object lies upon the principal axis (as it does in this example), then the image of this point will also lie upon the principal axis and be the same distance from the mirror as the image of the top of the object. At this point the complete image can be filled in. Intersection will give you the image location!

Concave Lens Let’s try! L: O: S: T:

Concave Lens Let’s try! L: O: S: T: L: O: S: T:

Concave Lens PROCESS BOX How does the LOST description compare for both of the images produced by concave lenses

convex lens = converging lens A convex lens is curved outward at the center and is thinnest at the outer edge. Convex lenses form either real or virtual images. If the object is located between a convex lens and its focal point it forms an enlarged virtual image If the object is located behind the focal point, it forms a smaller real image The real images is upside down. Example; microscopes, magnifying glasses, eye glasses. Convex lenses can be used to correct farsightedness when an eyeball is too short convex lens = converging lens

Object Behind Focal Point Object in front of Focal Point

Intersection will give you the image location! Convex Lens Convex Lens Diagrams Pick a point on the top of the object and draw two incident rays traveling towards the lens. Using a straight edge, accurately draw one ray so that it passes exactly through the focal point on the way to the lens. Draw the second ray such that it travels exactly parallel to the center line. Add arrowheads Intersection will give you the image location!

Intersection will give you the image location! Convex Lens Convex Lens Diagrams Once these incident rays strike the lens, refract them according to the rules of refraction for converging lenses. The ray that passes through the focal point will refract and travel parallel to the principal axis. The ray that traveled parallel to the principal axis on the way to the lens will refract and travel through the focal point. Place arrowheads upon the rays to indicate their direction Intersection will give you the image location!

Intersection will give you the image location! Convex Lens Convex Lens Diagrams Mark the image of the top of the object. If the bottom of the object lies upon the principal axis (as it does in this example), then the image of this point will also lie upon the principal axis and be the same distance from the mirror as the image of the top of the object. At this point the entire image can be filled in. Intersection will give you the image location!

Convex Lens L: O: S: T: Let’s try! L: O: S: T:

Convex Lens L: O: S: T: Let’s try! L: O: S: T:

Convex Lens PROCESS BOX How does the LOST description compare for both of the images produced by convex lenses?

Chapter 23

Convex (curves outward) Lenses – refract light Types of Lenses Images Formed Virtual or Real Direction of Image Concave (Curves inward) Virtual Upright/smaller Convex (curves outward) Object – Focal- Lens Real Upside down Convex (curves outward) Focal- Object- Lens Upright