Answer
0.34m
Work Step by Step
Use the lensmaker’s equation.
$$\frac{1}{f}=P=(n-1)(\frac{1}{R_1}+\frac{1}{R_2})$$
$$R_2=\frac{(n-1)R_1}{PR_1-(n-1)}$$
$$R_2=\frac{(1.56-1)(0.300m)}{(3.50D)(0.300m)-(1.56-1)}=0.34m$$
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