Mirrors and Lenses Mirrors and Lenses Sections 1

Mirrors and Lenses

Mirrors and Lenses Sections 1 -4 Flat Mirrors Images Formed by Spherical Mirrors Concave Mirrors and Sign Conventions Thin Lenses

Flat Mirrors The image formed by a plane mirror is upright, identical in size to the object, and as far behind the mirror as the object is in front of it.

Flat Mirrors The magnification is given by: For a plane mirror, M = +1.

Flat Mirrors What length is required for a full length mirror? B A

Flat Mirrors Multiple Images

Flat Mirrors Multiple Images

Images Formed by Spherical Mirrors A spherical mirror is a section of a sphere. It may be concave or convex.

Images Formed by Spherical Mirrors Concave Mirror Principle Focal Point

Mirrors and Lenses A light ray, traveling parallel to a concave mirror's axis, strikes the mirror's surface near its midpoint. After reflection, this ray (A) again travels parallel to the mirror's axis. (B) travels at right angles to the mirror's axis. (C) passes through the mirror's center of curvature. (D) passes through the mirror's focal point.

Images Formed by Spherical Mirrors Concave Mirror Light Source at the Focal Point Produces Parallel Rays of Light

Mirrors and Lenses A light ray, traveling obliquely to a concave mirror's surface, crosses the axis at the mirror's focal point before striking the mirror's surface. After reflection, this ray (A) travels parallel to the mirror's axis. (B) travels at right angles to the mirror's axis. (C) passes through the mirror's center of curvature. (D) passes through the mirror's focal point.

Images Formed by Spherical Mirrors We use ray diagrams to determine where an image will be. For mirrors, we use three key rays, all of which begin on the object: 1. A ray parallel to the axis; after reflection it passes through the focal point 2. A ray through the focal point; after reflection it is parallel to the axis 3. A ray perpendicular to the mirror; it reflects back on itself

Images Formed by Spherical Mirrors

Images Formed by Spherical Mirrors Concave Mirror Real Image

Images Formed by Spherical Mirrors For a concave mirror, the type of image formed depends on the position of the object.

Images Formed by Spherical Mirrors Concave Mirror Virtual Image

Images Formed by Spherical Mirrors The spherical-mirror equation is valid for any object position: Magnification:

Mirrors and Lenses A object is placed between a concave mirror and its focal point. The image formed is (A) virtual and inverted. (B) virtual and erect. (C) real and erect. (D) real and inverted.

Images Formed by Spherical Mirrors (Problem) A 2. 2 cm object is placed 15. 0 cm from a concave mirror with a radius of 25. 0 cm. (work on board) A) Where is the image located? B) What is its height? di = 75 cm h = -11 cm

Images Formed by Spherical Mirrors (Problem) A mirror at an amusement park shows an upright image of any person who stands 1. 4 m in front of it. If the image is three times the person’s height, what is the radius of curvature?

Mirrors and Lenses A light ray, traveling obliquely to a concave mirror's axis, crosses the axis at the mirror's center of curvature before striking the mirror's surface. After reflection, this ray (A) travels parallel to the mirror's axis. (B) travels at right angles to the mirror's axis. (C) passes through the mirror's center of curvature. (D) passes through the mirror's focal point.

Mirrors and Lenses If you stand in front of a concave mirror, exactly at its focal point, (A) you will see your image at your same height. (B) you won't see your image because there is none. (C) you will see your image, and you will appear smaller. (D) you will see your image and you will appear larger.

Images Formed by Spherical Mirrors Convex Mirror

Images Formed by Spherical Mirrors Convex Mirror Image will always be virtual do di f

Mirrors and Lenses If you stand in front of a convex mirror, at the same distance from it as its radius of curvature, (A) you won't see your image because there is none. (B) you will see your image at your same height. (C) you will see your image and you will appear smaller. (D) you will see your image and you will appear larger.

Mirrors and Lenses A single convex spherical mirror produces an image which is (A) always virtual. (B) always real. (C) real only if the object distance is less than f. (D) real only if the object distance is greater than f.

Images Formed by Spherical Mirrors

Images Formed by Spherical Mirrors Problem Solving: Spherical Mirrors 1. Draw a ray diagram; the image is where the rays intersect. 2. Apply the mirror and magnification equations. 3. Sign conventions: if the object, image, or focal point is on the reflective side of the mirror, its distance is positive, and negative otherwise. Magnification is positive if image is upright, negative otherwise. 4. Check that your solution agrees with the ray diagram.

Images Formed by Spherical Mirrors (Problem) A convex mirror (C = 90 cm) is used in your rearview mirror. Another car is 15 m from the mirror. (work on board) A) Where is the image located? B) What is its magnification? di = -0. 437 m M = 0. 0291 DOT requires C b/w 89 -165 cm

Thin Lenses Thin lenses are those whose thickness is small compared to their radius of curvature. They may be either converging (a) or diverging (b).

Mirrors and Lenses that are thicker at the center (A) spread out light rays. (B) bend light rays to a point beyond the lens. (C) have no effect on light rays. (D) reflect light rays back.

Thin Lenses Double Convex Lens Focal Point

Chapter 23 Mirrors and Lenses A light ray, traveling parallel to the axis of a convex thin lens, strikes the lens near its midpoint. After traveling through the lens, this ray emerges traveling obliquely to the axis of the lens (A) such that it never crosses the axis. (B) crossing the axis at a point equal to twice the focal length. (C) passing between the lens and its focal point. (D) passing through its focal point.

Thin Lenses Ray tracing for thin lenses is similar to that for mirrors. We have three key rays: 1. This ray comes in parallel to the axis and exits through the focal point. 2. This ray comes in through the focal point and exits parallel to the axis. 3. This ray goes through the center of the lens and is undeflected.

Thin Lenses

Thin Lenses Double Convex Lens Real Image

Thin Lenses For a diverging lens, we can use the same three rays; the image is upright and virtual.

Thin Lenses Concave Lens Virtual Focal Point

Thin Lenses

Thin Lenses The thin-lens equation: Magnification: Power: Lens power is measured in diopters, D. 1 D = 1 m-1

Thin Lenses Double Convex Lens

Mirrors and Lenses A convex lens has a focal length f. An object is placed between f and 2 f on the axis. The image formed is located (A) at 2 f. (B) between f and 2 f. (C) at f. (D) at a distance greater than 2 f from the lens.

Thin Lenses (Problem) A converging lens has a focal length of 20. 0 cm. (work on board) a) Locate the images for object distances of 40. 0 cm, b) Locate the images for object distances of 20. 0 cm. , c) Locate the images for object distances of 10. 0 cm.

Thin Lenses Concave Lens Virtual Image

Mirrors and Lenses The images formed by concave lenses (A) are always real. (B) are always virtual. (C) could be real or virtual; it depends on whether the object distance is smaller or greater than the focal length. (D) could be real or virtual, but always real when the object is placed at the focal point.

Thin Lenses (Problem) An object is placed 8 cm from a 20 cm converging lens. (work on board) A) What is the image distance? B) What is M? C) Type of image (real or virtual)? di = -13. 33 cm M = 1. 67 Virtual

Thin Lenses In lens combinations, the image formed by the first lens becomes the object for the second lens (this is where object distances may be negative).

Review of Chapter • Plane mirrors form virtual, upright, and unmagnified images. • The object distance is equal to the image distance. • The lateral magnification factor for all mirrors and lenses is: • Focal length of a spherical mirror:

Review of Chapter • Spherical-mirror equation: • Thin-lens equation:

homework - 1

Homework - 2

Homework - 3

Homework - 4

homework - 5

homework - 6