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Chapter 13 - PowerPoint PPT Presentation

Chapter 13 . Section 3 Curved Mirrors . Calculate distances and focal lengths using the mirror equation for concave and convex spherical mirrors. Draw ray diagrams to find the image distance and magnification for concave and convex spherical mirrors.

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Presentation Transcript

Chapter 13

Section 3 Curved Mirrors

• Calculate distances and focal lengths using the mirror equation for concave and convex spherical mirrors.

• Draw ray diagrams to find the image distance and magnification for concave and convex spherical mirrors.

• Distinguish between real and virtual images.

• Describe how parabolic mirrors differ fromspherical mirrors.

Objectives

Curved Mirrors

• Thus far in this unit, our focus has been the reflection of light off flat surfaces and the formation of images by plane mirrors. In Lessons 3 and 4 we will turn our attention to the topic curved mirrors, and specifically curved mirrors that have a sphericalshape. Such mirrors are called spherical mirrors. The two types of spherical mirrors are shown in the diagram on the right. Spherical mirrors can be thought of as a portion of a sphere that was sliced away and then silvered on one of the sides to form a reflecting surface

Types of curved mirrors

• A light off flat surfaces and the formation of images by plane mirrors. In Lessons 3 and 4 we will turn our attention to the concave spherical mirror is a mirror whose reflecting surface is a segment of the inside of a sphere.

• Concave mirrors can be used to form real images.

• A real image is an image formed when rays of light actually pass through a point on the image. Real images can be projected onto a screen.

Concave spherical mirror

Concave spherical mirror light off flat surfaces and the formation of images by plane mirrors. In Lessons 3 and 4 we will turn our attention to the

Concave spherical mirror

• If a concave mirror were thought of as being a slice of a sphere, then there would be a line passing through the center of the sphere and attaching to the mirror in the exact center of the mirror. This line is known as the principal axis. The point in the center of the sphere from which the mirror was sliced is known as the center of curvature and is denoted by the letter C in the diagram below. The point on the mirror's surface where the principal axis meets the mirror is known as the vertex and is denoted by the letter A in the diagram below. The vertex is the geometric center of the mirror. Midway between the vertex and the center of curvature is a point known as the focal point; the focal point is denoted by the letter F in the diagram below. The distance from the vertex to the center of curvature is known as the radius of curvature (represented by R). The radius of curvature is the radius of the sphere from which the mirror was cut. Finally, the distance from the mirror to the focal point is known as the focal length (represented by f). Since the focal point is the midpoint of the line segment adjoining the vertex and the center of curvature, the focal length would be one-half the radius of curvature.

Concave mirrors

Concave mirrors sphere, then there would be a line passing through the center of the sphere and attaching to the mirror in the exact center of the mirror. This line is known as the

• The Mirror Equation relates object distance ( sphere, then there would be a line passing through the center of the sphere and attaching to the mirror in the exact center of the mirror. This line is known as the p), image distance (q), and focal length (f) of a spherical mirror.

Mirror equation

• Unlike flat mirrors, curved mirrors forms images that are not the same size as the object. The measure of how large or small the image is with respect to the original object’s size is called the magnification of the image.

For an image in front of the mirror, m is negative and the image is upside down, or inverted

When the image is behind the mirror, M is positive and the image is upright with respect to the object

Magnification equation

Concave spherical mirrors

A the mirror and magnification equations for concave spherical mirrors.concave spherical mirror has a focal length of 10.0 cm. Locate the image of a pencil that is placed upright 30.0 cm from the mirror. Find the magnification of the image. Draw a ray diagram to confirm your answer.

Examples with concave mirrors

solution

Magnification equation object size.

15/30 =-1/2=-.5

solution

• A object size.convex spherical mirror is a mirror whose reflecting surface is outward-curved segment of a sphere.

• Light rays diverge upon reflection from a convex mirror, forming a virtual image that is always smaller than the object.

Convex spherical mirror

• Characteristic of convex mirror object size.

• A convex mirror is part of the outer surface of a hollow sphere

• A convex mirror produces diverged rays

• A convex mirror does not form real images

• Convex mirror in daily life, used in cars, and used in stores to observe shoppers.

Convex spherical mirrors

Convex mirror sample problem

Convex Mirrors mirror with a focal length of 8.00 cm. An erect image 2.50 cm tall is formed 4.44 cm behind the mirror. Find the position of the object, the magnification of the image, and the height of the pencil.

Given:

Because the mirror is convex, the focal length is negative. The image is behind the mirror, so q is also negative.

f = –8.00 cm q = –4.44 cm h’ = 2.50 cm

Unknown:

p = ? h = ?

• Using mirror equation

solution

Solve for p

p=.1 cm

Using magnification equation mirror with a focal length of 8.00 cm. An erect image 2.50 cm tall is formed 4.44 cm behind the mirror. Find the position of the object, the magnification of the image, and the height of the pencil.

M=-q/p

M=.444

M=h’/h

H=h’/m=5.63 cm

solution

• Three kinds of rays mirror with a focal length of 8.00 cm. An erect image 2.50 cm tall is formed 4.44 cm behind the mirror. Find the position of the object, the magnification of the image, and the height of the pencil.

• The ray parallel to the principal axis is reflected as if it is from focal point (f)

• The ray to focal point is reflected parallel to the principal axis

• The ray to the center of curvature C is reflected along its same path through C

Forming an image in convex mirrors

• Images created by spherical mirrors suffer from mirror with a focal length of 8.00 cm. An erect image 2.50 cm tall is formed 4.44 cm behind the mirror. Find the position of the object, the magnification of the image, and the height of the pencil.spherical aberration.

• Spherical aberration occurs when parallel rays far from the principal axis converge away from the mirrors focal point.

• Parabolic mirrors eliminate spherical aberration. All parallel rays converge at the focal point of aparabolic mirror.

Parabolic mirrors

Spherical aberration and parabolic mirror mirror with a focal length of 8.00 cm. An erect image 2.50 cm tall is formed 4.44 cm behind the mirror. Find the position of the object, the magnification of the image, and the height of the pencil.

• Do worksheet problems mirror with a focal length of 8.00 cm. An erect image 2.50 cm tall is formed 4.44 cm behind the mirror. Find the position of the object, the magnification of the image, and the height of the pencil.

Student guided practice

• Do problems 1-6 in your book page 462 mirror with a focal length of 8.00 cm. An erect image 2.50 cm tall is formed 4.44 cm behind the mirror. Find the position of the object, the magnification of the image, and the height of the pencil.

homework

• Today we learned about concave and convex mirrors mirror with a focal length of 8.00 cm. An erect image 2.50 cm tall is formed 4.44 cm behind the mirror. Find the position of the object, the magnification of the image, and the height of the pencil.

• Next class we are going to learn about color and polarization

Closure