Question

an object is kept in front of a concave mirror of Focal length of 15 cm, the image formed is 3 times the size of the object. calculate the two possible distance of the object From the mirror​

Answer 1

Answer:

Given that ; f = 15 cm

m = +3 (magnification)

u = ?

Now, calculating the distance of the object from the mirror (u),

we know, the mirror formula;

1/v + 1/u = 1/f

Here, m = +3, f = -15 cm

m = v/u = 3 therefore v =3u

1/f = 1/v + 1/u

1/-15 = 1/3u + 1/u

u = -20 cm

Hence, (u) = 20 is the distance of the object from the mirror.