Given,
R1 = 20 cm
R2 = 100 cm
Then focal length
\(f_1 = \frac {R_1}2\)
\(f_1 = \frac {20}2\)
f1 = 10 cm
So power of 20cm curvature radius lens
\(p_1= \frac{100} {f_1}\)
\(p_1= \frac{100} {10}\)
p1 = 10 D
For R2 = 100 cm
The focal length
\(f_2 = \frac {R_2}2\)
\(f_2 = \frac {100}2\)
f2 = 50 cm
Then power will be
\( p_2=\frac{100}{f_2}\)
\( p_2=\frac{100}{50}\)
p2 = 2 D