Answers

2016-03-17T17:19:16+05:30
B) 15
because R = 2f.
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2016-03-17T17:22:02+05:30
We know that focal length ( f ) is double of the Radius of curvature ( R )

⇒ R = 2f

if R = 30 cm 
    
   f =  30 ÷ 2

  f = 15 cm
1 5 1