Answer:
a ) 120 cm
size = 30 cm
b ) 12 cm from diverging lens
size = 12 cm
Explanation:
For converging lens
object distance u = - 40 cm
Focal length f = 30 cm
From lens formula
[tex]\frac{1}{v}-\frac{1}{u}=\frac{1}{f}
frac{1}{v}+\frac{1}{40}=\frac{1}{30}
v = 120 cm[/tex]
m=[tex]\frac{v}{u}[/tex]
m=[tex]\frac{120}{40}[/tex]
=3
Size of image = size of object x Magnification
= 3 x 10 = 30cm
For diverging lens
object distance u = 140 - 120 = 20 cm
focal length f = -30 cm
frac{1}{v}+\frac{1}{20}=-\frac{1}{30}
v = -12 cm
m = 12/20 = 0.6
size of final image = .6 x 30 = 18 cm