nuclear and particle physics

• What does the alpha source produce in Rutherford's experiment?

  Alpha particles
• What does the narrow beam of alpha particles hit in the experiment?

  A thin sheet of gold foil
• What did Rutherford observe about most alpha particles?

  They passed straight through the gold foil
• What does the observation of alpha particles passing through indicate?

  The nucleus is mostly empty space
• What does the deflection of very few particles at large angles suggest?

  The nucleus has a positive charge
• What is the purpose of estimating the size of the nucleus?

  To understand nuclear structure
• What happens to the alpha particle at the distance of closest approach?

  It has a speed of zero
• What is converted to electrical potential energy at closest approach?

  Kinetic energy of the alpha particle
• What is the kinetic energy of the particles used by Rutherford?

  7.7 mega electron volts
• How do you convert mega electron volts to joules?

  Multiply by $1.6 \times 10^{-13}$
• What is the approximate value of the kinetic energy in joules?

  Approximately $1.2 \times 10^{-12}$ joules
• What does the formula for potential energy involve?

  Charges and distance
• What is the formula for potential energy in this context?

  $U =$$\frac{qq}{4 \pi \epsilon_0 r}$
• What does $r$ represent in the potential energy formula?


  The distance of closest approach
• What is the charge of one gold nucleus?

  79 elementary charges
• What is the charge of the alpha particle?

  2 elementary charges
• What is the value of the elementary charge?

  $1.6 \times 10^{-19}$ coulombs
• What is the value of $\epsilon_0$ in the potential energy formula?


  $8.85 \times 10^{-12}$ F/m
• What is the estimated size of the nucleus?

  Approximately $3.0 \times 10^{-14}$ meters
• What is the range of estimated sizes for the nucleus?

  About $10^{-14}$ to $10^{-15}$ meters
• What does the nuclear model of the atom consist of?

  A nucleus and surrounding electrons
• What does the number $A$ represent in the nuclear model?


  Nucleon number
• How is the number of neutrons calculated?

  $N =$$A - Z$
• What is the atomic mass unit approximately equal to?

  $1.661 \times 10^{-27}$ kg
• What is the equation for nuclear size?

  $r =$$r_0 A^{1/3}$
• What is the value of $r_0$?


  $1.2 \times 10^{-15}$ meters
• How does the radius of the nucleus change with nucleon number?

  It increases with nucleon number
• What is the formula for density of the nucleus?

  $\rho =$$\frac{mass}{volume}$
• What is the volume of a nucleus assumed to be?

  A tiny sphere
• What is the density of most nuclei?

  Approximately $10^{17}$ kg/m³
• How does the density of the atom compare to the density of the nucleus?

  The atom's density is much lower
• Why is nuclear density independent of nucleon number?

  Mass is proportional to nucleon number
• What is the spacing between protons and neutrons in the nucleus?

  Similar regardless of the nucleus
• What is the distance between protons in helium?

  About $10^{-15}$ meters
• What force do protons in the nucleus experience?

  Electrostatic repulsive force
• What law is used to calculate the electrostatic force between protons?

  Coulomb's law
• What does Coulomb's law state about force?

  Force is proportional to charge and inversely to distance squared
• What is the approximate force between two protons in helium?

  Approximately 230 newtons
• What is the mass of a proton used in the force calculation?

  Approximately $1.6 \times 10^{-27}$ kg
• How does the force between protons compare to their mass?

  The force is very large compared to mass