A convex mirror always form virtual image, which is erect and small in size of an object kept in front of it.
Focal length of convex mirror f = + 15 cm
Object distance u = – 12 cm
Using mirror formula

1

v

+

1

u

=

1

f

1

v

+

1

−12

=

1

15

or

1

v

=

1

15

+

1

12

or

1

v

=

4+5

60

v = +

60

9

cm = + 6.66 cm
Therefore, image is virtual, formed at 6.67 cm at the back of the mirror.
Magnification m = -

v

u

m = -

60 9

−12

⇒ m =

5

9

= + 0.55
Size of image h2 = m × h1 =

5

9

×h1 =

5

9

× 4.5 ⇒ h2 = 2.5 cm
It shows the image is erect, small in size and virtual.
When the needle is moved farther from mirror the image also move towards focus and decreasing in size.
As u approaches ∞, v approaches focus but never beyond f.