Because a concave lens cannot form a real image of a real object, it is difficult to measure its focal length precisely. One method uses a second, convex, lens to produce a virtual object for the concave lens. Under the proper conditions, the concave lens will form a real image of the virtual object! A student conducting a laboratory project on concave lenses makes the following observations: When a lamp is placed 41.9 cm to the left of a particular convex lens, a real (inverted) image is formed 35.5 cm to the right of the lens. The lamp and convex lens are kept in place while a concave lens is mounted 13.5 cm to the right of the convex lens. A real image of the lamp is now formed 33.2 cm to the right of the concave lens. What is the focal length of the convex lens?
When I tried to do this problem I used the formula 1/f=1/di+1/do what I got 1.26 cm as my answer but it was wrong. what should I have done?
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