Sign Conventions in Different Lenses
The signs of the distances need to be carefully considered based on the type of lens. A short comparison for sign convention between convex and concave lens has been given below:
Convex Lens Sign Convention
For a convex lens, the sign convention is usually as follows:
- If the focal point (F) is on the left, it is positive.
- If the object is on the left side, the object distance (u) is positive.
- If the image is generated on the right side, the image distance (v) is positive.
Concave Lens Sign Convention
For a concave lens, the sign convention is usually as follows:
- There is a negative focal length.
- There is a negative image distance.
- There is never a positive object distance.
- From the optical centre of the lens to the right side, all measured distances are positive.
Read more about Difference Between Concave and Convex Lens.
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