The actual relationship between object distance and image distance is dependent upon the location of the object. Unlike plane mirrors, the object distance is not necessarily equal to the image distance. On the other hand, when the object is located between the center of curvature (C) and the focal point (F), the image is located beyond the center of curvature (C). When the object is located beyond the center of curvature (C), the image is located between the center of curvature (C) and the focal point (F). You might notice that while the same principle applies for determining the image location, a different result is obtained. By determining the path that light from the bulb takes after reflecting from the mirror, the image location can be identified. The image location is the location where reflected light appears to diverge from. If the light bulb is located at a different location, the same principles apply. The reflected light rays then begin to diverge, with each one being capable of assisting an individual in viewing the image of the object. The diagram below depicts several rays from the object reflecting from the mirror and converging at the image location. To view the image, the observer must line her sight up with the image location in order to see the image via the reflected light ray. Regardless of the observer's location, the observer will see a ray of light passing through the real image location. Not only is it the point where light rays converge, it is also the point where reflected light rays appear to an observer to be diverging from. The point where all the reflected light rays converge is known as the image point. Once the reflected light rays reach the image location, they begin to diverge. At the point where the light from the object converges, a replica, likeness or reproduction of the actual object is created. Upon reflecting, the light will converge at a point. Each individual ray of light that strikes the mirror will reflect according to the law of reflection. The light bulb will emit light in a variety of directions, some of which will strike the mirror. Suppose that a light bulb is placed in front of a concave mirror at a location somewhere behind the center of curvature (C). Only in the case of a real image, light is actually passing through the image location. When a real image is formed, it still appears to an observer as though light is diverging from the real image location. In this lesson we will begin to see that concave mirrors are capable of producing real images (as well as virtual images). Light does not actually pass through the virtual image location it only appears to an observer as though the light is emanating from the virtual image location. For plane mirrors, virtual images are formed. In Lesson 2, it was emphasized the image location is the location where reflected light appears to diverge from.

Lesson 2 discussed the formation of images by plane mirrors. This process is illustrated with two separate incident rays in the diagram at the right. Once the normal is drawn the angle of incidence can be measured and the reflected ray can be drawn with the same angle. For a concave mirror, the normal at the point of incidence on the mirror surface is a line that extends through the center of curvature. The task of determining the direction in which an incident light ray would reflect involves determining the normal to the surface at the point of incidence. Light always follows the law of reflection, whether the reflection occurs off a curved surface or off a flat surface.

Reflection definition photography