Formation of Images by Spherical Mirrors

1. Formation of Images by Spherical Mirrors

3. For an object infinitely far away (the sun or starts), the rays would be precisely parallel.

5. If a mirror is small compared to its radius of curvature, so that the reflected rays make only a small angle upon reflection, then the rays will cross each other at a single point, or focus.

6. The principal axis of a mirror is defined as the straight line perpendicular to the curved surface at its center.

7. The point F, where the rays parallel to the principal axis, come to a focus, is called the focal point of the mirror.

8. The distance between focal point and the center of the mirror is called the focal length, f, of the mirror.

9. Another way of defining the focal point is to say that it is the image point for an object infinitely far away along the principal axis.

10. Finding the Image Position for a Curved Mirror

11. ray 1 is drawn parallel to the axis; therefore it must pass along a line through F; • ray 2 is drawn through F, as result is must reflect into parallel to the principal axis ray; • ray 3 is chosen to be perpendicular to the mirror, and so is drawn so that it passes through C, the center of curvature; it will be reflected back on itself.

12. Mirror Equation

13. The lateral magnification, m, of a mirror is defined as the height of the image divided by the height of the object:

14. The Sign Convention • the image height hiis positive if the image is upright, and negative if inverted, relative to the object; • di and do are both positive if image and object are on the reflecting side of mirror, but if either image or object are behind the mirror, the corresponding distance is negative.