Benda setinggi 10 cm berdiri tegak didepan lensa cembung. Bila fokus lensa 20 cm dan jarak bayangan benda 30 cm, tentukan jarak benda terhadap lensa, perbesaran bayangan, tinggi bayangan

H = 10cm
f = 20cm
s' = 30cm
a. 1/f = 1/s + 1/s'
1/20 = 1/s + 1/30cm
1/20 – 1/30 = 1/s
3/60 – 2/60 = 1/s
1/60 = 1/s
60cm = s
b. M = |s'/s|
M = 30/60
M = 1/2 kali
c. M = |h'/h|
1/2 = |h'/10|
1/2 x 10 = h'
5cm = h'