(a) Concave lens.
(b) Optical centre.
(c) u = – 30 cm, f = 20 cm
(i) Using, 1/f = 1/v - 1/u we get,
1/v = (1/f +1/u = 1/20 +1/-30) = 3-2/60
= v 60 cm
Image is formed at a distance of 60 cm from the lens on the right side.
(iii) Image is real as v > 0, inverted and enlarged.