Answer:
30 cm
Explanation:
f = Focal length = 25 cm
R = Radius of curvature (both sides are equal)
= Refractive index of lens = 1.6
The lens maker formula is given by
minus sign because it is on the other side

The radius of curvature of the glass surface is 30 cm
Greater red shifts in the spectra of galaxies indicate faster speeds.