The ray of light diverges from the object; it is a real object. Focal length of a convex lens is positive.
(1/f) =[(n2-n1)/n1](2/R) = [(3/2) -1]/1(2/10) = 1/10
The given parameters are
u = -30 cm
f= +10 cm
substituting these values in thin lens equation, we have (1/v) – (1/u) = (1/f)
(1/v) – (1/-30) = (1/10)
which on solving gives v = +15 cm.
The image distance is positive, which implies that the image is real. The lateral magnification is
m = v/u = 15/(-30) = -1/2
The image is half the size of the object; size of the image is 0.50 cm.
The negative sign with magnification shows inverted image.