A person who can produce sharp images on their retina only of objects that lie from 80 cm to 240 cm from the eyes needs bifocal lenses. Assume that the bifocal lenses are worn 2 cm from the eye. a) Determine the desired optical power of the lens enabling them to see far objects. Is this lens concave or convex?

An alpha particle with kinetic energy 12.5 mev makes a collision with lead nucleus, but it is not "aimed" at the center of the lead nucleus, and has an initial nonzero angular momentum (with respect to the stationary lead nucleus) of magnitude l = p0 b, where p0 is the magnitude of the initial momentum of the alpha particle and b=1.40×10−12 m. (assume that the lead nucleus remains stationary and that it may be treated as a point charge. the atomic number of lead is 82. the alpha particle is a helium nucleus, with atomic number 2.) what is the distance of closest approach?