Physics - Geometrical Optics Question with Solution | TestHub

Focal length of a convex lens by displacement method Focal length of the convex lens $$f=\frac{a^2-b^2}{4a}$$ where $a$ = distance between the image and object and $b=$ distance between two positions of lens Fact The distance bemeen the ho points should be 4 times greater than the focal iength of the convex lens, ie, $d>4f$. So, the maximum possible focal length of this convex lens is $\frac{d}{4}$