Answer:
30 cm
Explanation:
f = Focal length = 25 cm
R = Radius of curvature (both sides are equal)
[tex]\mu[/tex] = Refractive index of lens = 1.6
The lens maker formula is given by
[tex]\frac{1}{f}=(\mu-1)(\frac{1}{R_1}-\frac{1}{R_2})\\\Rightarrow \frac{1}{f}=(\mu-1)(\frac{1}{R}-\frac{1}{-R})[/tex] minus sign because it is on the other side
[tex]\\\Rightarrow \frac{1}{f}=(\mu-1)\frac{2}{R}\\\Rightarrow R=2(\mu-1)f\\\Rightarrow R=2(1.6-1)\times 25\\\Rightarrow R=30\ cm[/tex]
The radius of curvature of the glass surface is 30 cm