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UNIT 8Light and Optics

Monday February 20th

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Light and Optics

TODAY’S AGENDA

Curved Mirrors ConvexHw: Practice C (even)

p466

UPCOMING…

Tue: Problem Quiz #1Color and Polarization

Wed: Refraction Thurs: Thin Lenses Biconvex Lens Fri: Thin Lenses Biconcave Lens Mon: Total Internal Reflection

Monday, February 20

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Chapter 13

Light and Reflection

Formation of Images by Spherical Mirrors

Spherical mirrors are shaped like sections of a sphere, and may be reflective on either the inside (concave) or outside (convex).

Formation of Images by Spherical Mirrors

Using geometry, we find that the focal length is half the radius of curvature:

Formation of Images 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 principal axis; after reflection it appears to come from the focal point.

2. A ray lines up with the focal point; after reflection it is parallel to the principal axis and appears to come from a position parallel behind the mirror.

3. A ray to the center of the mirror; after reflection it is the same angle to the principal axis. The principal axis

bisects the reflected angle. The ray appears to come from behind the mirror.

Convex Mirror

Images Formed by Spherical Mirrors

-f

do -di

Images Formed by Spherical Mirrors

Convex Mirror

Image Characteristics

Images Formed by Spherical Mirrors

Type: Real or Virtual

Size: Larger, Smaller, or Same (as the Object)

Orientation: Upright or Inverted

do: always positive

di: real is positive; virtual is negative

f: in front of mirror is positive; Behind mirror is negative

Images Formed by Spherical Mirrors

*Remember: for Convex mirrors, focal length is negative and distance of the image is negative.

Chapter 23 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.

The image of a distant tree is virtual and very small when viewed in a curved mirror. The image appears to be 18 cm behind the mirror. What kind of mirror is it, and what is its radius of curvature?

Images Formed by Spherical Mirrors (Problem)

Chapter 23 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

M = o

i

o

i

d

d

h

h

Magnification

M > 1 Larger

M < 1 Smaller

M + Upright

M - Inverted

M = 1 Same

-f

do -di

Convex Mirror

*Remember: for Convex mirrors, focal length is negative and distance of the image is negative.

Images Formed by Spherical Mirrors

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END