focal length of a concave mirror is 20cm and the image formed is 3times the size of the object. find the 2 possible values of the object.

Asked by  | 15th Feb, 2012, 10:31: PM

Expert Answer:

Case:1. Image is real. M = -3 Here f= -20 cm Now m=-v/u = -3 Or V = 3u From the mirror formula 1/f=1/u+1/v -1/20 = 1/u + 1/3u U=-80/3cm. Case:2. When the image is virtual m = 3 Now m = -v/u = 3 Or V=-3 From the mirror formula 1/f=1/u+1/v Then -1/20 = 1/u-1/3u 2/3u = -1/20 U=-40/3cm.

Answered by  | 16th Feb, 2012, 11:09: AM

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