Question

a concave mirror of focal length 20cm forms and virtual image whose size is 2.5 times the size of object find the object distance​

Answer 1

Answer:

u=(-1.2)cm

Explanation:

f=-20cm

m=+2.5

m= (-v)/u

u= (-v)/m -----(1)

1/f=1/v+1/u

1/(-20) = 1/v + 2.5/(-v)    {substituting

= (1-2.5)/v

==> v= (-1.5)*(-20)

= +30

from (1)

u=  -v/m

= -30/2.5

=-6/5

=  (-1.2)

Answer 2

Answer:

I'll tell u later

no need to tension