J.M. Gabrielse

Concave (just a part of a sphere)

J.M. Gabrielse

Concave Mirrors(caved in)

Examples include:• Shaving and makeup

mirrors

• Inside of a metal spoon

J.M. Gabrielse

optical axis

Concave Mirrors(caved in)

•F

Light rays that come in parallel to the optical axis reflect through the focal point.

J.M. Gabrielse

Concave Mirrors

Because concave mirrors are curved inward they reflect light rays in special way: reflected light rays travel toward each other, or converge.

J.M. Gabrielse

principal axis

Concave Mirror(when object is between focal point and mirror)

•F

J.M. Gabrielse

principal axis

Concave Mirror (when object is between focal point and mirror)

•F

The first ray comes in parallel to the principal axis and reflects through the focal point.

J.M. Gabrielse

principal axis

Concave Mirror (when object is between focal point and mirror)

•F

The first ray comes in parallel to the principal axis and reflects through the focal point.

The second ray comes through the focal point and reflects parallel to the principal axis.

J.M. Gabrielse

principal axis

Concave Mirror (when object is between focal point and mirror)

•F

The first ray comes in parallel to the principal axis and reflects through the focal point.

The second ray comes through the focal point and reflects parallel to the principal axis.

A third ray travels to the vertex and reflects at the same angle.

J.M. Gabrielse

principal axis

Concave Mirror (when object is between focal point and mirror)

The first ray comes in parallel to the principal axis and reflects through the focal point.

The second ray comes through the focal point and reflects parallel to the principal axis.

A third ray travels to the vertex and reflects at the same angle.

A virtual image forms where the sight rays converge.

•F

J.M. Gabrielse

principal axis

Your TurnConcave Mirror

(when object is between focal point and mirror)

•F

concave mirror

• Note: mirrors are thin enough that you just draw a line to represent the mirror• Locate the image of the arrow

object

J.M. Gabrielse

principal axis

Your Turn-AnswerConcave Mirror

(when object is between focal point and mirror)

•F

concave mirror

• Note: mirrors are thin enough that you just draw a line to represent the mirror• Locate the image of the arrow

object

J.M. Gabrielse

Characteristics of images in Concave Mirrors

(when an object is between the focal point and the mirror)

• S The image is larger than the object.• P The image distance is larger than the object

distance.• O The image is upright.• T The image is virtual (object's image lies behind

the mirror). 

J.M. Gabrielse

Concave Mirror(when object is between the focal point and 2 times the

focal point)

•F

•2F

principal axis

The first ray comes in parallel to the principal axis and reflects through the focal point.

J.M. Gabrielse

Concave Mirror(when object is between the focal point and 2 times the

focal point)

•F

•2F

principal axis

The first ray comes in parallel to the principal axis and reflects through the focal point.

The second ray comes through the focal point and reflects parallel to the principal axis.

J.M. Gabrielse

Concave Mirror(when object is between the focal point and 2 times the

focal point)

•F

•2F

principal axis

The first ray comes in parallel to the principal axis and reflects through the focal point.

The second ray comes through the focal point and reflects parallel to the principal axis.

A ray travels to the vertex.

A real image forms where the light rays converge.

J.M. Gabrielse

principal axis

Your TurnConcave Mirror

(when object is between the focal point and 2 times the focal point)

•Fobject

concave mirror

• Note: mirrors are thin enough that you just draw a line to represent the mirror• Locate the image of the arrow

•2F

J.M. Gabrielse

principal axis

Your Turn-AnswerConcave Mirror

(when object is between the focal point and 2 times the focal point)

•Fobject

concave mirror

• Note: mirrors are thin enough that you just draw a line to represent the mirror• Locate the image of the arrow

•2F

J.M. Gabrielse

Characteristics of Images in Concave Mirrors

(when object is between the focal point and 2 times the focal point)

• S The image is larger than the object.

• P The image distance is larger than the object distance.

• O The image is inverted.

• T The image is real (located in front of mirror)

J.M. Gabrielse

principal axis

Concave Mirror(when object is beyond 2 times the focal point)

•F

J.M. Gabrielse

principal axis

Concave Mirror (when object is beyond 2 times the focal point)

•F

The first ray comes in parallel to the principal axis and reflects through the focal point.

J.M. Gabrielse

principal axis

Concave Mirror (when object is beyond 2 times the focal point)

•F

The first ray comes in parallel to the principal axis and reflects through the focal point.

The second ray comes through the focal point and reflects parallel to the principal axis.

J.M. Gabrielse

principal axis

Concave Mirror (when object is beyond 2 times the focal point)

•F

The first ray comes in parallel to the principal axis and reflects through the focal point.

The second ray comes through the focal point and reflects parallel to the principal axis.

A real image forms where the light rays converge.

J.M. Gabrielse

principal axis

Your TurnConcave Mirror

(when object is beyond 2 times the focal point)

•Fobject

concave mirror

• Note: mirrors are thin enough that you just draw a line to represent the mirror• Locate the image of the arrow

J.M. Gabrielse

principal axis

Your Turn-Answer(Concave Mirror)

(when object is beyond 2 times the focal point)

•Fobject

concave mirror

• Note: mirrors are thin enough that you just draw a line to represent the mirror• Locate the image of the arrow

J.M. Gabrielse

Characteristics of Images in Concave Mirrors

(when object is beyond 2 times the focal point)

• S The image is smaller than the object.

• P The image distance is smaller than the object distance.

• O The image is inverted.

• T The image is real (located in front of mirror).

J.M. Gabrielse

Interactive Activity

See the effects of moving the object closer to the mirror, first between the center of curvature and the focal point, and then between the focal point and the mirror surface (to form a virtual image):

• http://micro.magnet.fsu.edu/primer/java/mirrors/concavemirrors/index.html

See how moving the object farther away from the center of curvature affects the size of the real image formed by the mirror:

• http://micro.magnet.fsu.edu/primer/java/mirrors/concavemirrors3d/index.html

J.M. Gabrielse

Can You Name Some Other Examples of Concave Mirrors?

Other examples of concave mirrors include:• spotlights, • flashlights, • overhead projectors, • car headlights, and• lighthouses.

J.M. Gabrielse

More Examples

• The largest telescopes all use concave mirrors to collect light because the mirror concentrates the light so effectively.

• Satellite dishes that receive television signals are curved dishes that reflect the microwaves coming from satellites.