Physics - Geometrical Optics Question with Solution | TestHub

Question No. 83 to 85 (Comprehension, 3 questions)

There is a very simple but very useful way to find the location of the image, its magnification and its properties in case of a lens or a mirror. Consider a concave mirror. Take a graph on the xy-plane as shown. The x-axis represents object distance ($u$) and the y-axis represents image distance ($v$). Consider a concave mirror with focal length $-10$ cm. Mark the point $(-10,-10)$ on the plane. For an object at $u=-20$ cm (by cartesian sign convention), draw a straight line from $x=-20$ to the y-axis such that it passes through $(-10,-10)$. The point at which it cuts the y-axis is the image; from the mirror formula as well as the geometry of the graph, $v=-20$ cm. Note that this is not a graph in the usual sense.