A stream of electrons accelerated by a potential difference V
falls on the surface of a metal whose inner potential is V 1 = 15 V.
Find:
(a) the refractive index of the metal for the electrons accelerated
by a potential difference V = 150 V;
(b) the values of the ratio 1//1/ i at which the refractive index differs
from unity by not more than r l -- 1.0%.