Question

when an object of height 1 cm is kept at a distance of 4 cm from a concave mirror it's erect image of height 1.5 cm is formed at a distance of 6 m in the mirror find the focal length of mirror​

Answer 1

1/v + 1/u = 1/f

1/ 6 + 1/-4 = 1/f. ( we apply minus because image produce backward

-2+3 / -12 = 1/f

1/-12= 1/f

f=-12

hope this is right thanks