CBSE Class 10 Answered
how much diameter of eyeball increases when person suffering from myopia or decreases when suffering from hypermetropia?
Derive lens formula & mirror formula
Asked by rkjsgr | 17 Jan, 2011, 12:00: AM
Expert Answer
Dear student
Pls. post each query individually.
Lens Maker's Formula |
It is a relation that connects focal length of a lens to radii of curvature of the two surfaces of the lens and refractive index of the material of the lens. |
The following assumptions are made for the derivation: |
The lens is thin, so that distances measured from the poles of its surfaces can be taken as equal to the distances from the optical centre of the lens. |
The aperture of the lens is small. |
Point object is considered. |
Incident and refracted rays make small angles. |
Consider a convex lens (or concave lens) of absolute refractive index m2 to be placed in a rarer medium of absolute refractive index m1. |
Considering the refraction of a point object on the surface XP1Y, the image is formed at I1 who is at a distance of V1. |
CI1= P1I1 = V1 (as the lens is thin) |
CC1 = P1C1 = R1 |
CO = P1O = u |
It follows from the refraction due to convex spherical surface XP1Y |
The refracted ray from A suffers a second refraction on the surface XP2Y and emerges along BI. Therefore I is the final real image of O. |
Here the object distance is |
(Note P1P2 is very small) |
(Final image distance) |
Let R2 be radius of curvature of second surface of the lens. |
\ It follows from refraction due to concave spherical surface from denser to rarer medium that |
Adding (1) & (2) |
Hope this clarifies your doubt.
Regards
Team
Topperlearning
Answered by | 18 Jan, 2011, 09:58: AM
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