Concave mirror concept:

A concave mirror in physics is a curved, semi-spherical mirror made either in the form of a segment of a sphere called a "spherical mirror" or in the form of a parabolic segment called a "parabolic mirror." If rays fell inside this mirror, the rays reflected on its curved surface and gathered at a point called a "focus". Or vice versa if we put a lamp in the focus of the mirror, then the rays are reflected on the surface of the concave mirror and leave it in the form of a parallel beam.

Uses of a concave mirror:

 A concave mirror is used in medicine and in the manufacture of lamps and car headlights and used to build observational telescopes.

Other metal types are used to receive television and radar waves, and we define them as a "tray" or "tray" for television reception. In this case, it collects the TV rays falling on it and coming from the TV station and collects them at a point where there is an amplifier that enlarges it and enters it to the TV to receive the image and sound.

The first to pay attention to the concave mirror:

Archimedes was interested in the concave mirror, just as al-Hasan ibn al-Haytham, an Arab scholar, conducted research on it and wrote about it.

Types of concave mirror:

A concave mirror works the same as a convex lens, and two types are used:

1) The spherical type: It is easy to make, but the image emerging from it is not a clear image because the parallel rays falling on the mirror core do not collect in one point, but they are collected in several points on the axis of the mirror, according to the reflections of light from the “head” of the sphere and from the parts of the mirror soon From the edge. This defect is called spherical clearance.

 Therefore, the concave mirror is produced in a second shape that needs great precision in manufacture because its surface is shaped in the form of a rotating parabola. This shape of the mirror was known during the seventeenth century, and it avoids the gathering of rays in the so-called spherical displacement, and combines the parallel rays falling on the mirror in one point, which is the focus.

2) Parabolic mirror: The mirror is in the form of a parabola. The incident rays parallel to the axis of the mirror are reflected in the focus, but manufacturing this mirror requires more effort than making a spherical mirror.

Spherical mirror:

The Cree surface industry can perform the function of a parabola mirror when the pellet radius is large, and this approximation is sufficient for many uses. And it is easier to manufacture a spherical mirror than making a mirror in the form of a parabola, so that the spherical mirror is exploited in many cases.

The optical properties of a concave mirror depend on the pellet radius. If we put a lamp in the center of the mirror pellet, the rays reflected from the surface of the mirror collects again at the point where the lamp is. This is because every ray incident on the surface of the spherical mirror falls perpendicular to it and is reflected on itself, and the reflected rays collect again at the center of the globule. But in the event that parallel rays fall from infinity on the surface of the spherical mirror, they collect in focus. This focus is approximately at the radius of the pellet. That is, the “focal length” of a concave mirror is equal to one-half of the “pellet radius”. But the rays collected from the globular mirror cannot be collected at one point, due to the globular displacement. The rays reflected from different rings of the mirror collect at one point other than the other.

What does a spherical mirror consist of ??

Each spherical mirror has several components, which are as follows:

• Mirror pole: It is the center of the mirror surface.
• The center of the mirror ball: It is the center of the ball that the mirror is part of. This center comes behind the convex mirror and in front of the concave mirror.
• The main axis of the mirror: called the optical axis, and it is the straight line that connects the pole of the mirror and its center.
• Mirror focus: It is the point at which the reflected rays collect when parallel rays fall on the surface of the mirror.
• Mirror focal length: It is the distance between the pole of the mirror and its focal length, and it is part of the main axis of the mirror.