HELP!!! opted physics question #39

[116903]

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can anyone solve this problem for me?
😳

 

[Frank101]

1/f=1/r+1/r'

Given r & r' (30cm & 6cm respectably)

1/f=1/30+1/6

1/f=0.0333+0.16
1/f=0.1933

Take the inverse

f=1/0.1933
f=5.17 or approx f=5 (Answer C)

 

[EyEnStein 07]

post question next time =/

 

[116903]

thank you very much.