How Do You Calculate The Focal Point Of A Concave Mirror?
Rays of light shining directly at a concave mirror, perpendicular to its surface if it were a plane mirror, will reflect at an angle. No matter where such light strikes the mirror or at what angle it is reflected, that reflected light will pass through a single point in front of the mirror. This point is called the focus. Mathematically, the focus is halfway between the surface of the mirror and what would be the center if the mirror formed a complete circle; it can be thought of as half the distance to the radius. Place the object in front of the mirror so that its reflection appears upright. (If you place the object too far back–behind the focus–then the image will appear upside down.) Measure the distance from the object to the mirror, and record this distance as “p.” Multiply p times the magnification of the mirror. Multiply this distance by “-1,” and record the answer as “i.” Physically, i represents the distance between the mirror and the virtual image formed by reflection. The
