#importing modules
import math
from __future__ import division
#Variable declaration
N=6.02*10**23; #avagadro number(atoms/mole)
rho=19.3; #density(g/cc)
A=197; #atomic weight(g)
k=8.984*10**9; #value of k(Nm**2/C**2)
Z=79;
Zdash=2;
e=1.6*10**-19; #conversion factor from J to eV
m=2;
v0=8*10**6;
t=2*10**-6; #thickness(m)
#Calculation
n=N*rho*10**6/A; #number of atoms(per m**3)
b=k*Z*Zdash*e/(m*v0); #impact parameter(m)
f=math.pi*b**2*n*t; #fraction of particles scattered
#Result
print "fraction of particles scattered is",round(f*10**5,1),"*10**-5"
#importing modules
import math
from __future__ import division
#Variable declaration
h=6.626*10**-34; #planck's constant(Js)
c=3*10**8; #velocity of light(m/sec)
e=1.6*10**-19; #conversion factor from J to eV
E=10.5; #energy(eV)
#Calculation
E=(13.6+E)*e; #energy of photon(J)
lamda=h*c/E; #wavelength(m)
#Result
print "wavelength of photon is",round(lamda*10**9,2),"nm"
#importing modules
import math
from __future__ import division
#Variable declaration
k=8.98*10**9; #value of k(Nm**2/C**2)
e=1.6*10**-19; #conversion factor from J to eV
n=1; #assume
a0=0.53*10**-10; #radius of orbit(m)
#Calculation
PE=-k*(e**2)/(a0*e*n**2); #potential energy(eV)
E=-13.6/n**2; #energy(eV)
KE=E-PE; #kinetic energy(eV)
#Result
print "kinetic energy is",round(KE,1),"/n**2 eV"
#importing modules
import math
from __future__ import division
#Variable declaration
Mbyme=1836;
lamda=6562.8; #wavelength for hydrogen(angstrom)
#Calculation
mew_dashbymew=2*(1+Mbyme)/(1+(2*Mbyme));
lamda_dash=lamda/mew_dashbymew; #wavelength for deuterium(angstrom)
#Result
print "wavelength for deuterium is",int(lamda_dash),"angstrom"