Question

a object is placed in front of a concave mirror of focal length 20 cm the image formed is 3 times the size of the object calculate two possible distance of the object from the mirror​

Answer 1

Answer:

given image is 3 times that of object. so there is 2 case: image is real , inverted and magnified OR the image is virtual , erect and magnified. so m= 3 or -3 . hence v = 3u or v = -3u . f = -15 cm (given). Using mirror formula:

1/u+1/3u = -1/15 gives u = -20 cm.

OR

1/u - 1/3u = -1/15 gives u = -10 cm.

I hope it helps you.