You are thinking of a concave (converging) mirror, not a lens.InFiNitY1 said:In school physics i have learned that the focus for a circular convex(converging) lens is f=r/2 where r is the radius and f is focus.
Of course. The focal length of a lens depends on the refractive index as well as the curvature of the surfaces:But wouldn't a pair of identical lens made of a different material eg glass and perspecs which have different refractive indexes have different point of focus?
The purpose of having the same focus for all circular lenses is to ensure that all incoming light rays converge at a single point. This allows for a clear and focused image to be formed.
Having the same focus for all circular lenses helps to improve the image quality by reducing spherical aberration. This means that all points on the image will be in focus, resulting in a sharper and more accurate representation of the object being viewed.
No, it is not necessary for all circular lenses to have the same focus. For example, in a camera lens, the different elements may have different focal lengths to achieve different effects such as zooming or blurring.
One potential disadvantage of having the same focus for all circular lenses is that it can limit the flexibility in the design and use of the lenses. For certain applications, it may be beneficial to have different focal lengths for different lenses.
Scientists use precision manufacturing techniques and rigorous testing procedures to ensure that all circular lenses have the same focus. This includes shaping the lens to specific curvatures and using specialized equipment to measure and adjust the focal length as needed.