1. The problem statement, all variables and given/known data There is a small shiny object in a big aquarium, which is formed like a cuboid and filled with water. The plan site of a plano-convex lens with a focal length f is put on the wall of the aquarium from outside. The object is located on the optical axis of the lens. The refraction index of water is 1.33, the index of the lens is 1.50. The wall of the aquarium and the less are very thin. Consider only rays which are located nearly to the optical axis. a) Determine the position of the image of the object as function of the position of the object. Name in each case, whether it is a virtual or a real, an upright or a turned, an enlarged or shrinked image. b) Calculate the image distance and the enlargemet if the object distance has a value of 2.5*f. c)Do the sam as in b) BUT now the lens is put on the wall from inside (again with plan side). 2. Relevant equations n1*sin(a)=n2*sin(b) 3. The attempt at a solution First of all, we imagine that th wall does not exist. My idea was to consider an object as point (-xo , yo). Now we have to look at the ray which is parallel to the axis: It will refracted at the crossing between air and lens and it will cross the optical lens at the point (f , 0). We can describe this ray after refraction with the function f(x)=yo-yo/f*x. Moreover we have to consider the ray which crosses the lens in the point (0 , 0). I failed at determining the function g(x) which is the ray after being refracted. The intersection point of f(x) and g(x) should be the image, right?