Mirrors are reflective surfaces that bounce light back in predictable ways. There are two main types of curved mirrors: concave mirrors, which curve inward like the inside of a spoon, and convex mirrors, which curve outward like the back of a spoon. A flat mirror reflects light at the same angle it receives it. A concave mirror converges parallel light rays to a focal point in front of the mirror. A convex mirror diverges light rays, making them appear to come from a virtual focal point behind the mirror.
Concave mirrors curve inward like the inside of a spoon. They have several important properties. First, they converge parallel light rays to a focal point in front of the mirror. The focal point is located halfway between the mirror and its center of curvature. When light rays from an object hit the mirror, they follow predictable paths. Rays parallel to the principal axis reflect through the focal point. Rays passing through the center of curvature reflect back along the same path. Rays through the focal point reflect parallel to the principal axis. Where these reflected rays intersect, an image forms. Depending on where the object is placed, concave mirrors can form real or virtual, upright or inverted, and magnified or diminished images. Concave mirrors are commonly used in telescopes, microscopes, makeup mirrors, car headlights, and solar concentrators.
Convex mirrors curve outward like the back of a spoon. Unlike concave mirrors, convex mirrors diverge parallel light rays, making them appear to originate from a virtual focal point behind the mirror. This focal point is located at half the radius of curvature. When light rays from an object hit a convex mirror, they reflect outward. Rays parallel to the principal axis reflect as if coming from the focal point. Rays directed toward the center of curvature reflect parallel to their incident path. Where these reflected rays appear to intersect behind the mirror, a virtual image forms. Convex mirrors always produce virtual, upright, and reduced images regardless of the object's position. One key advantage of convex mirrors is their wide field of view, allowing them to show more area than flat mirrors of the same size. This makes them ideal for side-view mirrors on vehicles, security mirrors in stores, blind spot mirrors, and ATM surveillance.
The type of image formed by a mirror depends on both the mirror type and the object's position. Let's explore how images form in a concave mirror as we move an object to different positions. When the object is beyond the center of curvature C, the image is real, inverted, and reduced in size. When the object is at the center of curvature, the image is real, inverted, and the same size as the object. As we move the object between the center of curvature and the focal point, the image becomes real, inverted, and enlarged. When the object is exactly at the focal point, no image forms because the reflected rays become parallel and never converge. Finally, when the object is between the focal point and the mirror surface, we get a virtual, upright, and enlarged image. In contrast, convex mirrors always form virtual, upright, and reduced images regardless of where the object is placed. The image size decreases as the object moves farther from the mirror. This consistent behavior, combined with their wide field of view, makes convex mirrors ideal for security and driving applications.
To summarize what we've learned about curved mirrors: Concave mirrors curve inward like the inside of a spoon and converge light rays to a focal point in front of the mirror. They can form either real or virtual images depending on the object's position. Concave mirrors are used in applications like telescopes, makeup mirrors, and car headlights. Convex mirrors, on the other hand, curve outward like the back of a spoon and diverge light rays, making them appear to come from a virtual focal point behind the mirror. They always form virtual, upright, and reduced images, providing a wider field of view than flat mirrors. This makes them ideal for security mirrors, side-view mirrors on vehicles, and other applications where a wide viewing angle is important. The key difference between these mirror types lies in how they reflect light and the types of images they form, which determines their practical applications.