Object distance, u = +12 cm (virtual object)
(a) Focal length of the convex lens, f = 20 cm
Image distance = v
Applying lens formula
1/v – 1/u = 1/f
Therefore putting the values and solving the equation, we get v = 60/8 i.e. = 7.5 cm
Hence, the image is formed 7.5 cm away from the lens, toward its right.
(b) Focal length of the concave lens, f = -16
again image distance = v
the again as previous, applying the lens formula, substituing the values of u and f, we get v= 48 cm.
Hence, the image is formed 48 cm away from the lens, towards its right.
