4.1 The Concepts of Force and Mass

Chapter 25The Reflection of Light: Mirrors25.1 Wave Fronts and Rays

A hemispherical view ofa sound wave emitted by apulsating sphere.

The rays are perpendicularto the wave fronts.25.1 Wave Fronts and Rays

At large distances from the source, the wave fronts become lessand less curved.25.2 The Reflection of Light

LAW OF REFLECTION

The incident ray, the reflected ray, and the normal to the surface all lie in the same plane, and the angle of incidence equals the angle of reflection.25.2 The Reflection of Light

In specular reflection, the reflected rays are parallel to eachother.ConcepTest 26.1ReflectionWhen watching the Moon over the ocean, you often see a long streak of light on the surface of the water. This occurs because:1) the Moon is very large2) atmospheric conditions are just right3) the ocean is calm4) the ocean is wavy5) motion of the Moon6ConcepTest 26.1ReflectionWhen watching the Moon over the ocean, you often see a long streak of light on the surface of the water. This occurs because:1) the Moon is very large2) atmospheric conditions are just right3) the ocean is calm4) the ocean is wavy5) motion of the Moon

725.3 The Formation of Images by a Plane Mirror

The persons right hand becomesthe images left hand.

The image has three properties:

It is upright.It is the same size as you are.The image is as far behind the mmirror are you are in front of it.25.3 The Formation of Images by a Plane Mirror

A ray of light from the top of the chess piece reflects from the mirror.To the eye, the ray seems to come from behind the mirror.

Because none of the rays actually emanate from the image, it iscalled a virtual image.25.3 The Formation of Images by a Plane Mirror

The geometry used to show that the image distance is equalto the object distance.25.3 The Formation of Images by a Plane Mirror

Conceptual Example 1 Full-Length Versus Half-Length Mirrors

What is the minimum mirror height necessary for her to see her fullimage?25.3 The Formation of Images by a Plane Mirror

Conceptual Example 2 Multiple Reflections

A person is sitting in front of two mirrors that intersect at a right angle.The person sees three images of herself. Why are there three, ratherthan two, images?ConcepTest 26.2Mirror ISO1234mirrorAn observer at point O is facing a mirror and observes a light source S. Where does the observer perceive the mirror image of the source to be located?13ConcepTest 26.2Mirror ISO1234mirrorAn observer at point O is facing a mirror and observes a light source S. Where does the observer perceive the mirror image of the source to be located?14ConcepTest 26.3Mirror IIYou stand in front of a mirror. How tall does the mirror have to be so that you can see yourself entirely?1) same as your height2) less than your full height but more than half your height 3) half your height 4) less than half your height 5) any size will do

15ConcepTest 26.3Mirror IIYou stand in front of a mirror. How tall does the mirror have to be so that you can see yourself entirely?1) same as your height2) less than your full height but more than half your height 3) half your height 4) less than half your height 5) any size will do

16Makenzie walks directly toward a plane mirror at a speed of 0.30 m/s. Determine the speed of the image relative to her.

A) 0.15 m/sB) 0.30 m/sC) 0.60 m/sD) 0.90 m/sMakenzie walks directly toward a plane mirror at a speed of 0.30 m/s. Determine the speed of the image relative to her.

A) 0.15 m/sB) 0.30 m/sC) 0.60 m/sD) 0.90 m/sFive balls labeled A, B, C, D, and E are placed in front of a plane mirror as shown in the figure. Which ball(s) will the observer, in the position shown, see reflected in the mirror?

A) A onlyB) C onlyC) A and BD) A, B, D and EE) A, B, C, D and EFive balls labeled A, B, C, D, and E are placed in front of a plane mirror as shown in the figure. Which ball(s) will the observer, in the position shown, see reflected in the mirror?

A) A onlyB) C onlyC) A and BD) A, B, D and EE) A, B, C, D and E25.4 Spherical Mirrors

If the inside surface of the spherical mirror is polished, it is a concavemirror. If the outside surface is polished, is it a convex mirror.

The law of reflection applies, just as it does for a plane mirror.

The principal axis of the mirror is a straight line drawn through thecenter and the midpoint of the mirror.25.4 Spherical Mirrors

A point on the tree lies on the principal axis of the concave mirror.Rays from that point that are near the principal axis cross the axisat the image point.25.4 Spherical Mirrors

Light rays near and parallel to the principal axis are reflectedfrom the concave mirror and converge at the focal point.

The focal length is the distance between the focal point andthe mirror.

25.4 Spherical Mirrors

The focal point of a concave mirror is halfway betweenthe center of curvature of the mirror C and the mirror at B.

25.4 Spherical Mirrors

Rays that lie close to the principal axis are called paraxial rays.

Rays that are far from the principal axis do not converge to a single point. The fact that a spherical mirror does not bring all parallel rays to a single point is known as spherical abberation.25.4 Spherical Mirrors

When paraxial light rays that are parallel to the principal axis strike a convex mirror, the rays appear to originate from the focalpoint.25.5 The Formation of Images by Spherical MirrorsCONCAVE MIRRORS

This ray is initially parallel to the principal axisand passes through the focal point.This ray initially passes through the focal point,then emerges parallel to the principal axis.This ray travels along a line that passes through the center.25.5 The Formation of Images by Spherical Mirrors

Image formation and the principle of reversibility25.5 The Formation of Images by Spherical Mirrors

When an object is located between the focal point and a concave mirror,and enlarged, upright, and virtual image is produced.If you stand in front of a concave mirror, exactly at its focal point,A) you won't see your image because there is none.B) you won't see your image because it's focused at a different distance.C) you will see your image, and you will appear smaller.D) you will see your image and you will appear larger.E) you will see your image at your same height.If you stand in front of a concave mirror, exactly at its focal point,A) you won't see your image because there is none.B) you won't see your image because it's focused at a different distance.C) you will see your image, and you will appear smaller.D) you will see your image and you will appear larger.E) you will see your image at your same height.An object is placed at a concave mirror's center of curvature. The image produced by themirror is locatedA) out beyond the center of curvature.B) at the center of curvature.C) between the center of curvature and the focal point.D) at the focal point.An object is placed at a concave mirror's center of curvature. The image produced by themirror is locatedA) out beyond the center of curvature.B) at the center of curvature.C) between the center of curvature and the focal point.D) at the focal point.

25.5 The Formation of Images by Spherical MirrorsCONVEX MIRRORSRay 1 is initially parallel to the principal axis and appears to originate fromthe focal point.

Ray 2 heads towards the focal point, emerging parallel to the principal axis.

Ray 3 travels toward the center of curvature and reflects back on itself.25.5 The Formation of Images by Spherical Mirrors

The virtual image is diminished in size and upright.25.6 The Mirror Equation and Magnification

25.6 The Mirror Equation and Magnification

These diagrams are usedto derive the mirror equation.

25.6 The Mirror Equation and MagnificationExample 5 A Virtual Image Formed by a Convex Mirror

A convex mirror is used to reflect light from an object placed 66 cm infront of the mirror. The focal length of the mirror is -46 cm. Find the locationof the image and the magnification.

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 won't see your image because it's focused at a different distance.C) you will see your image and you will appear smaller.D) you will see your image and you will appear larger.E) you will see your image at your same height.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 won't see your image because it's focused at a different distance.C) you will see your image and you will appear smaller.D) you will see your image and you will appear larger.E) you will see your image at your same height.Sometimes when you look into a curved mirror you see a magnified image (a great big you) and sometimes you see a diminished image (a little you). If you look at the bottom (convex) side of a shiny spoon, what will you see?A) You won't see an image of yourself because no image will be formed.B) You will see a little you, upside down.C) You will see a little you, right side up.D) You will see a little you, but whether you are right side up or upside down depends on how near you are to the spoon.E) You will either see a little you or a great big you, depending on how near you are to thespoon.Sometimes when you look into a curved mirror you see a magnified image (a great big you) and sometimes you see a diminished image (a little you). If you look at the bottom (convex) side of a shiny spoon, what will you see?A) You won't see an image of yourself because no image will be formed.B) You will see a little you, upside down.C) You will see a little you, right side up.D) You will see a little you, but whether you are right side up or upside down depends on how near you are to the spoon.E) You will either see a little you or a great big you, depending on how near you are to thespoon.25.6 The Mirror Equation and MagnificationSummary of Sign Conventions for Spherical Mirrors