Answer: The total magnification = -3.0
Explanation:
Since the lenses are in contact, the combined focal length, f, of the two lenses is given by,
1/f = 1/f₁ + 1/f₂, where f₁ and f₂ are the focal lengths of the two lenses.
1/f = 1/20 + 1/-30
1/f = (-3 + 2)/-60 = -1/-60
1/f = 1/60
f = 60cm
magnification = image distance/object distance = v/u
where u = 40cm, v = ?
Using the mirror, 1/f = 1/v + 1/u
1/60 = 1/v + 1/40
1/v = 1/60 - 1/40
1/v = ( 2 - 3)/120 = -1/120
v = -120cm
Therefore, magnification = -120cm/40cm
magnification = -3.0
