Jarak fokus cermin cekung 10 cm. Tentukan letak, perbesaran dan sifat bayangan dari benda yang terletak di depan cermin sejauh 15 cm

A ) Diket.
f = 10 cm
s = 25 cm

Maka, Jarak bayangan..
1/f = 1/s + 1/s'
1/10 = 1/25 + 1/s'
1/s' = 1/25 - 1/10 = 2/50 - 5/50
1/s' = 50 cm
Dan perbesaran...
M = s'/s
M = 50/25
M = 2 Kali

b ) Diket
f = 10 cm
s = 10 cm

Maka, jarak bayangan...
1/f = 1/s + 1/s'
1/s' = 1/10 - 1/10
1/s' = 10 cm
Dan perbesaran...
M = s'/s
M = 10/10
M = 1 kali

c ) Diket
f = 19 cm
s = 5 cm

Maka, jarak bayangan...
1/f = 1/s + 1/s'
1/s' = 1/10 - 1/5 = 1/10 - 2/10
1/s' = -1/10 = 10 cm
Dan perbesaran...
M = s'/s
M = 10/10
M = 1 kali