20.4 - Spherical mirrors

Convex and concave mirrors are segments of spherical mirror surfacesThe image in a flat mirror is a life-size, undistorted “picture” of the original object. The image in a curved mirror may be upside-down, magnified, or distorted in other ways. The simplest curved mirror to analyze has the shape of a section of a sphere. Think of a shiny, hollow ball—and then cut off a piece of it. A convex mirror has a reflecting surface that bulges outward. A concave mirror has a reflecting surface that cups inward, like a bowl. Read the text aloud
Reflection in spherical mirrors
The reflecting surface of a spherical mirror is a segment of the surface of a sphere. The center of curvature of the mirror is the center of the sphere. The radius of curvature of the mirror is the radius of the sphere. Read the text aloud
Incident light rays reflect about the normal to the surface of the mirrorThe law of reflection applies to reflection from a curved surface. The normal, however, has a different direction at each location on the surface. The normal to any point on the surface of a spherical mirror is a radial line that goes from the center of curvature through that point. In the figure at right, an incident ray striking the mirror at an angle of 25° to the normal reflects at an angle of 25° on the opposite side of the normal. Read the text aloud
Diverging and converging mirrors
Consider the same series of parallel light rays incident upon two different spherical mirrors. The reflected rays from the convex mirror diverge from each other. A convex mirror is therefore called a diverging mirror. The side rear-view mirrors on a car are slightly convex. The divergence provides a wider field of view compared to a flat mirror, causing objects to look farther away than they actually are. Read the text aloud
The reflected rays from the concave mirror come together or converge with each other. A concave mirror is a converging mirror. The focusing mirror of a solar oven is a converging mirror. Large astronomical telescopes use concave mirrors. The ability to see distant objects depends on collecting as much light as possible. It is far easier to create a large-diameter, optically perfect mirror than it is to make an optically perfect lens of equal size. Read the text aloud Show Reflected rays and the focal point
A curved lens is part of a sphere with a diameter of 3 m. How far from the lens is the center of curvature?
  1. 1.5 meters
  2. 3 meters
  3. 4.5 meters
  4. 6 meters

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