# what is focal length and radius of curvature of a concave lens ?

santhosh
67 Points
9 years ago
Focal Length and Radius of Curvature
concave mirror
convex mirror
Consider a ray of light AB, parallel to the principal axis, incident on a spherical mirror at point B. The normal to the surface at point B is CB and CP = CB = R, is the radius of curvature. The ray AB, after reflection from mirror will pass through F (concave mirror) or will appear to diverge from F (convex mirror) and obeys law of reflection, i.e., i = r.
From the geometry of the figure,

If the aperture of the mirror is small, B lies close to P, \ BF = PF
or FC = FP = PF
or PC = PF + FC = PF + PF
or R = 2 PF = 2f

Similar relation holds for convex mirror also. In deriving this relation, we have assumed that the aperture of the mirror is small.

SHANMUKESHWAR
461 Points
9 years ago
Focal Length and Angle of view. The focal length of the lens is the distance between the lens and the image sensor when the subject is in focus, usually stated in millimeters (e.g., 28 mm, 50 mm, or 100 mm). In the case of zoom lenses, both the minimum and maximum focal lengths are stated, for example 18–55 mm.
the radius of a circle which touches a curve at a given point and has the same tangent and curvature at that point.
Concave lenses are thinner at the middle. Rays of light that pass through the lens are spread out (they diverge). A convex lens is a diverging lens. When parallel rays of light pass through a concave lens the refracted rays diverge so that they appear to come from one point called the principal focus.
PRAPULPODISHETTI
669 Points
9 years ago
Focal Length:
The distance of principle focus from optic center is called focal length of aconcave lens.
The radius of the sphere of which the curved surface of the lens forms a part is called the radius of curvature of a concave lens. A concave lens has two radii of curvatures
kalyan
184 Points
9 years ago
Focal Length: The distance of principle focus from optic center is called focal length of a
concave lens.
Radius of Curvature: The radius of the sphere of which the curved surface of the lens forms
a part is called the radius of curvature of a concave lens. A concave lens has two radii of
curvatures.

AJITH
118 Points
9 years ago
The distance of principle focus from optic center is called focal length of a concave lens. The radius of the sphere of which the curved surface