A biconvex lens is formed by using a piece of plastic (n=1.7)the radius of the front surface is 20cm and the radius of the backsurface is 30cm. What is the focal length of the lens?
There must be some formula to do this or something i know f=r/2 but does that mean you add the radii together or am i supposeto individually find each focal point and add them together?
like (.3/2) + (.2/2) = .25 which makesnot much sense. So if you know the secret to this onepleasee helpp!