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.
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