# Sign Convention For Lens Maker Formula

Sign Convention For Lens Maker Formula. This formula only works for thin lenses. If we suppose that the lens is exceedingly narrow (d = 0). we may simplify the equation as follows:

Lens Sign Convention 11.Sign Convention Lens Formula from elishabrahg.blogspot.com

For converging lenses. the focal length is always positive. while diverging lenses always have negative focal lengths. Sign convention is very important for setting up the geometric relations that are used to derive the lens maker’s formula. and also for substituting the values in the final equation to obtain the focal length of the lens. N 2 v − n 1 u = n 2 − n 1 r.

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In any derivation of geometrical optics. we use the sign convention twice: The lens focal length is given by the lens maker formula :

But also. therefore. we can say that. where μ is the refractive index of the material. For refraction at a curved surface:

The radii of curvature here are measured according to the cartesian sign convention. On violation of the limitations then the refraction at the curved surface formula is used for both the surfaces.

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The lens focal length is given by the lens maker formula : In the derivation of lens makers formula.

For converging lenses. the focal length is always positive. while diverging lenses always have negative focal lengths. A lens has two foci. f and f′. on either side of it.

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For refraction at a curved surface: Once while deriving it and next while using it for general cases.

#### There Is A Sign Convention That We All Must Follow While Using The Lens Maker’s Formula.

$\frac 1 f= \frac 1 {s}+\frac 1 s$ this will only give you correct results. if you follow the correct sign conventions. The radii of curvature r_1 and r_2 may be positive or negative depending on the shape of the surfaces of the diopters constituting the lens. The lens focal length is given by the lens maker formula :

#### In Any Derivation Of Geometrical Optics. We Use The Sign Convention Twice:

Lets derive the famous lens makers formula. Is the first surface lets call that radius of curvature as r 1 r 1 now you may be curious as to why were not using sign conventions at all all talk a little bit more about that later on but this is what we got for surface number 1 lets call it as equal. But while deriving lens makers formula. we dont consider negative and positive values of the radius of curva

#### The Refractive Index Of The Material Of The Lens A Can Be Introduced Into The Lens Formula.

Sign convention is very important for setting up the geometric relations that are used to derive the lens maker’s formula. and also for substituting the values in the final equation to obtain the focal length of the lens. 1 f = ( n 2 n 1 − 1) [ 1 r 1 − 1 r 2] 1 f = ( μ − 1) [ 1 r 1 − 1 r 2] where. μ is the refractive index of the medium. For converging lenses. the focal length is always positive. while diverging lenses always have negative focal lengths.

#### The Complete Derivation Of Lens Maker Formula Is Described Below.

If we dont use sign convention. we can use the the derived formula in only the. So the thin lens formula equation : The distances measured along the direction of the incident light are considered positive. while the distances in the opposite direction are negative.

#### The Radii Of Curvature Here Are Measured According To The Cartesian Sign Convention.

This is because the separation between the two refracting surfaces will also be small. This is the expression of the lens maker’s formula. Once while deriving it and next while using it for general cases.