Lens Maker’s formula
The Lens Maker’s Formula is an equation used to relate the focal length of a lens to its physical characteristics, such as its curvature and refractive index. This formula applies specifically to thin lenses, which are lenses that have negligible thickness compared to their radii of curvature. The equation is given by:
1/f = (μ-1)(1/R1-1/R2)
Where,
- f is the focal length of the lens.
- μ is the refractive index of the lens material.
- R1 is the radius of curvature of one surface of the lens.
- R2 is the radius of curvature of the other surface of the lens.
Note: If a surface is convex (curved outward), its radius of curvature is taken as positive and if surface is concave (curved inward), its radius of curvature is taken as negative.
Read more about Lens Maker’s Formula.
Magnification Formula
The magnification formula for a lens is given by:
m = h/h′ = −u/v
Where,
- m represents the magnification.
- h′ is the height of the image.
- h is the height of the object.
- v is the image distance.
- u is the object distance.
Power of Lens
The power of a lens is a measure of its ability to bend light, and it’s expressed in diopters (D). The power of a lens depends on its focal length f, and the formula to calculate it is:
P = 1/f
Where:
- P represents the power of the lens in diopters (D).
- f is the focal length of the lens in meters (m).
Lens Sign Convention
A lens in optics is a transparent device with curved surfaces that refract light. It can be converging or diverging based on its shape. The lens sign convention, or Cartesian sign convention, helps determine the nature, size, and position of images formed by lenses accurately. It clarifies the positive and negative signs for object and image distances, focal lengths, and magnifications, crucial for optical calculations and predictions.
Table of Content
- What is the Lens Sign Convention?
- Basics of Lens Sign Convention
- Cartesian Sign Convention
- Sign Conventions in Different Lenses
- Lens Maker’s formula
- Conclusion: Lens Sign Convention