# Images formed by concave mirror of objects placed between center and focus do not end up as expected

I am more involved with mechanics at this moment, but my sister in 7th grade pointed out that when objects placed in between center and focus of a concave mirror are 'too big' the simple two ray diagrams (the diagrams in which two rays are drawn originating from a common point of an object, one parallel to the principal axis, other passing through focus) don't behave as expected. The image should be bigger than the object, and outside the center of curvature but when the object taken is too big, this does not work. Is there a law at work that I am not aware of? I will try to model the concave mirror, taking parameters as the height of the object, radius of curvature of mirror and distance of the object from the.mirror's pole to give out the height and.position of the image, but the it might take time to develop the idea.

• Could you add an expected ray diagram so we can understand a bit bitter? And maybe even a photo of the actual observation. – BMS Jan 5 '15 at 19:08
• If nothing else, the approximation that is involved, i.e. that a circular mirror is almost like a parabola, fails when you get beyond a height equal to the radius. – Carl Witthoft Jan 5 '15 at 20:17
• @CarlWitthoft Thank you. I had no idea about that assumption, trying to model the concave mirror would have been a waste of time. – user1512179 Jan 6 '15 at 20:00