Posted by J on .
The crystalline lens of the human eye is a double convex lens made of material haveing an index of refraction of 1.44. Its focal length in air is about 8 mm which also varies. We shall assume that the radii of curvature of its two surfaces have the same magnitude. (a) Find the radii of curvature of this lens. (b) if an object 16 cm tall is placed 30 cm from the eye lens where would the lens focus it and how tall would the image be? is this image real or virtual? erect or inverted?
I cant figure out part a, I have an equation but I am confused. Help please!

Physics 
drwls,
The focal length f of a biconvex lens is given by
1/f = (n1) (1/R1  1/R2)= 2(n1)/R if the two radii of curvature both equal R and the curvatures are in opposite directions.
1/8 = 2*(0.44)/R
R = 7.04 cm