E=mc^2 solve for c e/m m/e sqrt(e/m) sqrt(m/e) e - m sqrt(e-m)

E = m c²

Divide each side by 'm':  E/m = c²

Take the square root of each side: c = √(E/m)

concave lenses are used here. they spread the light out before it reaches the convex lens in the eye, therefore letting the image focus directly on the retina. hyperopia is known to you probably as farsightedness.