Jawabanmu

2014-06-15T12:33:10+07:00
Jawab :
Bikonveks 
R1 = R2= +40 cm 
n = 1,65 

1/f = (n-1)[1/R1 + 1/R2) 
1/f = (0,65)[2/40] 
f = 30,769 cm atau 31 cm <-- 

semoga membantu :)
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