Consider a nonionized phosphorus donor atom in a si crystal.
(a) what is the "bohr radius" of the resulting "atom? "
(b) estimate how many si atoms are contained within a sphere of this "bohr radius"?
(c) estimate how high the concentration of impurities would have to be for the "bohr radii" to overlap, and what would you expect to happen in this case?

An electron moves with a constant horizontal velocity of 3.0 × 106 m/s and no initial vertical velocity as it enters a deflector inside a tv tube. the electron strikes the screen after traveling 26 cm horizontally and 19 cm vertically upward with no horizontal acceleration. what is the constant vertical acceleration provided by the deflector? (the effects of gravity can be ignored.)