# Where is the focal point on a concave mirror?

The geometric center of the mirror is represented by the vertex. The focal point is a location located halfway between the vertex and the center of curvature; the focal point is symbolized by the letter F in the picture below. An image is formed at this location, regardless of how the mirror is oriented.

Concave mirrors have one advantage over convex mirrors: You can place objects closer to them than you can to convex mirrors. This is because there's no shadow circle for objects behind the mirror.

Another difference between convex and concave mirrors is that you can see through a convex mirror but not necessarily all the way to the other side. With a concave mirror, you can see clear to the end of the tube where the glass meets the frame.

A third difference is that objects near the focus appear larger than they do outside of it. This is because everything gets magnified by the same factor near the lens. So if something is twice as far away as another thing, it will appear four times as large.

Outside of the lens, close objects appear small and distant objects look far away. Inside the lens, all objects look like they're close up.

Finally, an object near the axis of a convex mirror appears to be upright, but one near the edge appears upside down.

## What is the point where the principal axis meets the mirror?

The vertex is the point on the mirror's surface where the primary axis meets the mirror, and it is symbolized by the letter A in the diagram. Because the vertex is not fixed, it will move whenever you lift up or put down the mirror.

There are two types of vertices: flat and curved. A flat vertex does not reflect light; rather, it forms one end of a straight line on the surface of the mirror. A curved vertex reflects light; instead, it forms one end of a curve on the surface of the mirror. A prismatic mirror has flat vertices, while a parabolic mirror has curved vertices.

A flat vertex allows you to see objects that are beyond the range of the mirror. For example, if there's a person standing behind a curtain at the other end of the room when you first walk into the house, you can see them with a flat-sided mirror. They won't be in clear view once you lift your head, but that person would be hidden from view if the mirror had a rounded corner.

A curved vertex improves your ability to see detail within close range. If there's something interesting near the corner of a wall, for example, you can watch it unfold itself into view as you approach.

## What is the distance between the focal point and the mirror?

Finally, the focal length is the distance between the mirror and the focus point (represented by f). The focal length would be one-half the radius of curvature since the focal point is the midway of the line segment connecting the vertex and the center of curvature.

Therefore, the distance from the focus point to the mirror is equal to the radius of curvature times the focal length. In this case, it's about 3 meters.

The focus point is about 2 meters from the corner reflector. To put it another way, the focal length of a corner reflector is about 3 meters.

## What is the center of curvature in a mirror?

The mirror's center of curvature is the center of the sphere from which it is sliced. The pole of the mirror is the aperture's halfway. The plane of the mirror is perpendicular to its surface.

A convex lens has its center of curvature on the side closer to the camera. A concave lens has its center of curvature on the far side. If you look at both lenses from the front, they appear symmetrical but that's because you're looking at them from the opposite side. The center of curvature is always on the same side as the aperture. If the lens has multiple centers of curvature, say two, then one is near the aperture and one is farther away.

Mirrors and lenses are the only optical elements with fixed positions regarding height above or below the axis of vision. All other elements can be moved relative to each other for focusing purposes; this includes eyes and objects within view. For example, when you look through the viewfinder of your camera, the lens focuses objects by moving toward them or away from the camera body.

Because mirrors do not focus images, they must be positioned so that whatever you are trying to reflect comes inside their field of regard.

## What is the pole of a mirror?

It is the center of the concave mirror's reflecting surface, also known as the mirror's vertex, and is commonly symbolized by the letter "P." The letter "C" represents the center of the sphere, of which the concave mirror is a part. Although not visible in this diagram, the pole of a convex mirror is located on its opposite side from the center.

The word "pole" comes from Latin polus, meaning "spoke," because of its connection with the wheels of a chariot. In astronomy, a celestial body's axis forms a polar axis if it is equally distant from all other celestial bodies. The Earth's axis is its only polar axis. All other planets have two or three major axes, which are nearly parallel to one another. The poles are the points on any planet that are closest to or furthest from its center.

The term "mirror image" is often used to describe an object where you would expect to find a duplicate of itself but instead finds a copy of its reflection. If you look into a mirror and say "hello," then someone else looking at you would say "hello" back.

## Where is the object located when the image produced by a concave mirror is simply a dot?

The item is not at the middle of the curve. The red arrows in this image indicate the locations of the items in front of the concave mirror. Because there is no other thing in the picture to reflect light into the camera, the only thing that can be seen with the naked eye is the book. However, if you look closely at the photo, you can make out two dots on the wall behind the book.

##### Diana Bowles

Diana Bowles is a professor. She has a PhD in Education and English Literature. Diana teaches at an elementary school, and she loves her job because it allows her to share her love for learning with children each day. She volunteers as the president of the PTA at her school, where she spends time helping other parents find their voice to advocate for what they believe in.

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