Question

Can there be an element with atomic mass 53 and 54 in between the two element, chromium and managanese

Answer 1

The lens flexes to change its curvature and finish the focusing process. When an object is located at infinity, the focal length, or the distance from the cornea to the retina, of a normal relaxed eye is about 1.7 cm (17 mm). Clark, R.N. Notes on the Resolution and Other Details of the Human Eye.