19.1 Mirrors The smooth surface of the lake reflects light rays so that the observer sees an...

19.1 Mirrors

The smooth surface of the lake reflects light rays so that the observer sees an inverted image of the landscape.

19.1 Mirrors

What is the law of reflection?

The Law of Reflection

The law of reflection states that the angle of reflection is equal to the angle of incidence.

19.1 Mirrors

The angle of incidence is the angle the incident ray makes with a line drawn perpendicular to the surface of the mirror.

The angle of reflection is the angle the reflected ray makes with the perpendicular line.


19.1 Mirrors

The study of optics assumes that light is made up of rays that travel in straight lines.

• A ray diagram shows how rays change direction when they strike mirrors and pass through lenses.

• A mirror reflects an incident ray, making a reflected ray.


19.1 Mirrors

The flat (plane) mirror and the mirror-like lake surface both obey the law of reflection.

The Law of Reflection Incident ray

Angle of incidence

Angle of refraction

Refracted ray

19.1 Mirrors

What type of image is produced by a plane mirror?

Plane Mirrors

A plane mirror always produces a virtual image.

19.1 Mirrors

A virtual image is a copy of an object formed at the location from which the light rays appear to come.

A mirror with a flat surface is a plane mirror. When you look into a plane mirror, you see your reversed reflection—a right-left reversed image of yourself.

Plane Mirrors

19.1 Mirrors

To produce your image in a mirror, rays of light strike you and reflect.

• The reflected rays strike the mirror and are reflected to your eyes.

• The rays appear to come from behind the mirror. • Your image appears the same distance behind

the mirror as you are in front, and the image is right side up.

Plane Mirrors

19.1 Mirrors

Virtual images such as this cannot be projected onto a screen. Note also how that light rays from the object (the girl) reflect from the mirror’s surface and obey the law of reflection.

Plane Mirrors

19.1 Mirrors

What type of image is produced by convex and concave mirrors?

Concave and Convex Mirrors

Concave mirrors can form either real or virtual images.

Convex mirrors always cause light rays to spread out and can only form virtual images.

19.1 Mirrors

Concave Mirrors

When the inside surface of a curved mirror is the reflecting surface, the mirror is a concave mirror.

• The curvature of the reflecting surface causes the rays to come together.

• The point at which the light rays meet is called the focal point.

Concave mirrors in automobile headlights and flashlights direct the illumination from a light bulb into a beam.


19.1 Mirrors

The type of image formed depends upon where the object is in relation to a concave mirror. When the object is farther from the mirror than the focal point, the reflected rays meet in front of the mirror to form a real image.

• A real image is a copy of an object formed at the point where light rays actually meet.

• Unlike a virtual image, a real image can be viewed on a surface such as a screen.


19.1 Mirrors

When the object is closer to the mirror than the focal point is, the reflected rays spread out and appear to come from behind the mirror to form a virtual image.


19.1 Mirrors

A. Parallel incoming rays are reflected through the focal point of a concave mirror.


Focal point

Concave mirror

19.1 Mirrors

B. Real images form when the reflected light rays converge.


Focal point

Concave mirror

19.1 Mirrors

C. Virtual images form when the reflected rays appear to come from a point behind the mirror.


Focal point

Concave mirror

19.1 Mirrors

Convex Mirrors

When the outside surface of a curved mirror is the reflecting surface, the mirror is a convex mirror.

• The curvature of the convex mirror causes the reflected rays to spread out. The image formed by a convex mirror is always upright and smaller than the object.

• A convex mirror shows a wide angle of view. • Convex mirrors can only form virtual images.


19.1 Mirrors


A. Parallel incoming rays are reflected away from one another by a convex mirror.

Focal point

Convex mirror

19.1 Mirrors

B. The virtual images are upright and smaller than the object.


Focal point

Convex mirror

19.1 Mirrors

Assessment Questions

1. The image in a plane mirror appears to be a. in front of the mirror.

b. behind the mirror.

c. in the plane of the mirror.

d. perpendicular to the plane of the mirror.

19.1 Mirrors


1. The image in a plane mirror appears to be a. in front of the mirror.

b. behind the mirror.

c. in the plane of the mirror.

d. perpendicular to the plane of the mirror.

ANS: B

19.1 Mirrors


2. A real image formed by a mirror is a. always right-side up. b. always smaller than the object.c. able to be projected on a screen.d. only formed by convex mirrors.

19.1 Mirrors


2. A real image formed by a mirror is a. always right-side up. b. always smaller than the object.c. able to be projected on a screen.d. only formed by convex mirrors.

ANS: C

19.1 Mirrors


3. An image of an object, formed by a convex mirror, is always a. upright and smaller than the object.

b. upside down and smaller than the object.

c. upright and larger than the object.

d. upside down and larger than the object.

19.1 Mirrors


3. An image of an object, formed by a convex mirror, is always a. upright and smaller than the object.

b. upside down and smaller than the object.

c. upright and larger than the object.

d. upside down and larger than the object.

ANS: A

19.1 Mirrors


1. According to the law of reflection, the angle of reflection is equal to the angle of incidence.

TrueFalse

19.1 Mirrors


1. According to the law of reflection, the angle of reflection is equal to the angle of incidence.

TrueFalse

ANS: T

19.1 Mirrors The smooth surface of the lake reflects light rays so that the observer sees an...

Documents

Transcript of 19.1 Mirrors The smooth surface of the lake reflects light rays so that the observer sees an...