EXAMPLE PROBLEMS: QUESTIONS: 1) An object is placed at a distance of 20 cm from a concave mirror of focal length 10 cm. Then find image distance and nature of the image. ANS: Mirror type: concave Given data, u=-20 cm( “-“ is because of sign convention, object distance should be measured from pole to object which is in opposite Direction to the direction of incident ray) f=-10 cm ( applying sign convention same as above) mirror formula => 1/f=1/u+1/v ð 1/-10=(1/-20)+(1/v) ð 1/v=(1/20)+(1/-10) ð 1/v=(1/20)-(1/10) ð 1/v=(1-2)/20 (on taking L.C.M) ð 1/v=-1/20 ð V=-20 cm Nature: Here “-“ sign indicates the image formed is real and inverted. The image is formed on the object itself as the object distance and image distance are equal. The image is formed at C. (refer case 3 of concave mirror) 2) ...
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