Optical instruments use a converging lens, most frequently for changing the direction of light. The next type of lens most frequently used is the diverging lens. The first lens type, also known as a positive lens, bends all light rays entering parallel to the optical axis towards the axis, converging to a common point, the focal point F. A diverging lens, also termed a negative lens, directs the rays away from the axis. They appear to be emanating from the focal point F of the lens, except when the ray lies on the optical axis. Both cases are indicated.
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