Question

An object is placed a distance of 6 cm from a concave mirror and having an image distance 3 cm. The focal length of the image is…

Answer 1

Answer:

1/f=1/v+1/u ,. .... here object distance is -6cm, image distance two possiblity is -3,+3 . first use -3cm . 1/f= -1/3+(-1/6). 1/f = -2-1/6 ,, ‌‌1/f=-3/6 , f is -2 cm . ,. then v is +3cm, 1/f=1/3+(-1/6) ... 1/f =1/3-1/6 ,,,,,1/f = 2-1/6 then f is +6 cm and it is wrong because focal length of concave mirror is always negative . so f is -2 cm and v is -3 cm