3.6: Mirrors & 3.6: Mirrors & LensesLenses

12/15/14

Part 1: MirrorsA.Light is necessary for eyes to see

1. Light waves spread in all directions from a light.2. The brain interprets light waves as traveling in a

straight line.B.Plane mirror—flat, smooth mirror

1. Light strikes an object and is reflected off the object to the mirror and then back to the object.

2. Virtual image—no light waves pass through the image

C. Concave mirror—mirror surface is curved inward1. Optical axis—imaginary straight

line drawn perpendicular to the center of the mirror’s surface

2. Focal point—point on the optical axis through which parallel light rays are reflected

3. Distance from the mirror center to the focal point is the focal length.

4. Real images—light rays converge to form the image5. If an object is at the focal point, a concave mirror reflects

light rays in a beam.6. An object farther from the concave mirror than the focal point

forms a real, enlarged, and inverted image.

6. An object farther from the concave mirror than the focal point forms a real, enlarged, and inverted image.

7. An object between the focal point and the concave mirror forms a virtual, upright, and enlarged image.

D. Convex mirror—mirror is curved outward1. Light rays diverge when they are reflected.2. Images are virtual, upright, and smaller

than the actual object.

mirror type exampleimages produced by light rays ___

the image formed is ___

under these conditions:

CONCAVEinside of spoon (curved inward) converging

real, enlarged, and inverted

when the image is farther from the mirror than the focal point

virtual, upright, and enlarged

when the image is between the focal point and the mirror

CONVEXsecurity camera mirror (curved

outward)diverging virtual, upright,

and smaller always

1. Light rays diverge when they are reflected.2. Images are virtual, upright, and smaller than the actual object.

mirror type exampleimages produced by light rays ___

the image formed is ___

under these conditions:

CONCAVEinside of spoon (curved inward) converging

real, enlarged, and inverted

when the image is farther from the mirror than the focal point

virtual, upright, and enlarged

when the image is between the focal point and the mirror

CONVEXsecurity camera mirror (curved

outward)diverging virtual, upright,

and smaller always

Part 2: LensesA.Lens—transparent material with a

curved surface that refracts light raysB.Convex lens—thicker in the middle

than at the edges1. When an object is more than two focal lengths from the lens,

its image is real, reduced, and inverted.2. When an object is between one and two focal lengths from

the lens, its image is real, enlarged, and inverted.3. When an object is less than one focal length from the lens, its

image is virtual, enlarged, and upright.

1. When an object is more than two focal lengths from the lens, its image is real, reduced, and inverted.

2. When an object is between one and two focal lengths from the lens, its image is real, enlarged, and inverted.

3. When an object is less than one focal length from the lens, its image is virtual, enlarged, and upright.

1.

2.

3.

C. Concave lens—thinner in the middle and thicker at the edges; forms a virtual, upright, reduced image

D. Lenses in eyeglasses can help the eyes focus on objects.1. Cornea—transparent covering on eyeball2. Retina—inner lining of the eye that

converts light into electrical signals that the brain interprets as images

3. The lens in the eye changes shape to focus on near and far objects.

E. Vision problems occur when lenses do not focus images properly.1. Farsighted people’s lenses do not curve enough to form an

image of close objects; convex lenses converge incoming light rays before they enter the eye.

2. Astigmatism occurs when the cornea’s surface is unevenly curved; corrective lenses can cancel out the effects of the unevenness.

2. Astigmatism occurs when the cornea’s surface is unevenly curved; corrective lenses can cancel out the effects of the unevenness.

3. Nearsighted people’s lenses do not flatten enough to form an image of distant objects; concave lenses can spread out incoming light rays before they enter the eye.

lens type exampleimages produced by light rays ___

the image formed is ___

under these conditions:

CONCAVEglasses for

nearsightedness (curved inward)

converging virtual, upright, and smaller always

CONVEXglasses for

farsightedness (curved outward)

diverging

real, inverted, and smaller

when object is located beyond 2 focal points from the lens

real, inverted, and larger

when object is located between 1 and 2 focal points from the lens

virtual, upright, and larger

when object is located within 1 focal point from the lens