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

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

## 5 Answers

7 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.

7 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.

7 years ago

Focal Length:

The distance of principle focus from optic center is called focal length of aconcave 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

7 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.

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.

7 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