Question

An object of size 7.5 cm is placed in front of a convex mirror of radius of curvature 25 cm at a distance of 40 cm.the size o he image should be...........................

Answer 1

f=25/2 cm
u= -40 cm
mirror formula,
1/v +1/u =1/f
⇒1/v= 2/25 - (1/(-40))
⇒1/v = 2/25+ 1/40
         =21/200
⇒v=200/21 cm
now, magnification = h'/h = -(v/u)
⇒h'/7.5= -(200/(21×(-40))
⇒h' =25/17 =1.47 cm
so the image is virtual and diminished 

Answer 2

Answer:1.78 cm

Explanation:as we know,focal length=radius of curvature/2

u= - 40cm

So we get f=25/2

1/v + 1/u = 1/f

1/v = 2/25+1/40

v=200/21

Now m= -v/u=height of image/height of object

200/21×40=height of image/7.5

So

Height of image is 1.78 cm