Some basic terms regarding the spherical mirror

 

Some basic terms regarding the spherical mirror:--

 

Pole:--

           The center of the reflecting surface of the spherical mirror is a point.

Pole is represented by the letter P. and it lies on the surface of the mirror.

 

Center of a curvature:--

                                         The center of a curvature is a point of the reflecting surface of the  spherical mirror that forms a part of the sphere and this sphere has a center is known as center of a curvature.

It is denoted by the letter C. in the concave mirror, the center of a curvature lies in front of the mirror. And in the convex mirror , the center of curvature lies behind the mirror.

 

Radius of a curvature:--

                                         Radius of curvature is the point in which the radius of the sphere of which the reflecting surface of a spherical mirror form is a part is called as the radius of curvature. It is denoted by the letter R. and it is the linear distance between the pole and the center of a curvature.

 

Principal axis :--

                           Principal axis is a imaginary straight line passing through the pole and the center of a curvature of a spherical mirror is called as principal axis.

 

Principal Focus of spherical mirror :--

                                                              The principal focus of the spherical mirror is a point on the principal axis of the spherical mirror where the ray of light parallel to the principal axis actually converge or diverge after reflection is called as principal axis of the spherical mirror. It is denoted by the letter F.

The principal focus of spherical mirror is a point on the principal axis at which the ray of light which are parallel to the principal axis actually converge or diverge after reflection from the mirror.

 

Principal focus of concave mirror:-

                                                            A number of ray of light  parallel to the principal axis that falls on the concave mirror, and get reflected. And these reflected light rays intersecting or meeting at a principal axis of the mirror. This point is called as principal focus of the concave mirror.

A number of light rays that are parallel to the principal  axis of a concave mirror that falls on the concave mirror that get converged at a particular point on its principal axis after reflection from the mirror. This point is called as principal focus of the concave mirror.

 

Principal focus of convex mirror:-

                                                              principal focus of convex mirror is a point on the principal axis where light rays that are parallel to the principal axis appears to be diverge from the mirror.

A number of ray of light parallel to the principal axis that falls on the concave mirror, and get reflected. And these reflected light rays appears to come from a point on the  principal axis of the mirror. This point is called as principal focus of the convex mirror.

 

                                                        

 

                                                         

                                                             

Focal length :--

                         Focal lenth is the distance between the focus and the pole is called as focal length. It is denoted by the letter f.

 

Focal plane:--

                    When a ray of light is incident near the pole of the mirror and created an angle, then the reflected ray of light is appeared to be converged or diverged from a plane. That is perpendicular to the principal axis through principal focus F. this plane is called as focal plane.

Focal plane is the plane that passes through the principal focus and perpendicular to the principal axis.

Aperture:--

                   The diameter of the reflecting surface of the spherical mirror is called as aperture.

It is the portion of the spherical mirror from which the reflection of light takes place.

 

Relationship between the radius of the curvature (R) and focal length (f) of a spherical mirror.

The radius of the curvature is to be equal to the twice of the focal length.

R =  2f

This implies that the principal focus of a spherical mirror lies between the pole and the center of the curvature.

 

When a light reflected by the concave mirror on the sheet of paper held close to the mirror. The paper begins to burn and producing smoke.

Reason:-- in the concave mirror, the light rays from the sun is converged at a point which is sharp, bright spot by the mirror. In fact, this spot of light rays of the sun is the image of the sun that concentrates on the sheet paper. And this point is the focus of the concave mirror. Due to concentration of the sun rays  on the paper sheet, the heat is produced that ignites the paper. And the distance of this image from the position of the mirror provides the approximately value of the focal length of the mirror.