α-particle

Examples of α-particle in the following topics:

• Nuclear Size and Density

  • The famous Rutherford gold foil experiment involved the scattering of α-particles by gold foil, with some of the particles being scattered through angles of more than 90°, that is coming back to the same side of the foil as the α-source, as shown in Figure 1.
  • Top: Expected results: alpha particles passing through the plum pudding model of the atom undisturbed.Bottom: Observed results: a small portion of the particles were deflected, indicating a small, concentrated positive charge.

• Gamma Decay

  • When a nucleus emits an α or β particle, the daughter nucleus is usually left in an excited state.
  • In certain cases, the excited nuclear state following the emission of a beta particle may be more stable than average; in these cases it is termed a metastable excited state if its decay is 100 to 1000 times longer than the average $10^{-12}$ seconds.

• Scattering of Light by the Atmosphere

  • Rayleigh scattering is the elastic scattering of waves by particles that are much smaller than the wavelengths of those waves.
  • The particles that scatter the light also need to have a refractive index close to 1.
  • The formula to calculate the intensity of the scattering for a single particle is as follows:
  • where I is the resulting intensity, I0 is the original intensity, α is the polarizability, λ is the wavelength, R is the distance to the particle, and θ is the scattering angle.
  • Describe wave-particle relationship that leads to Rayleigh scattering and apply it to explain common phenomena

• Alpha Decay

  • In alpha decay an atomic nucleus emits an alpha particle and transforms into an atom with smaller mass (by four) and atomic number (by two).
  • Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle that consists of two protons and two neutrons, as shown in .
  • Because an alpha particle is the same as a helium-4 nucleus, which has mass number 4 and atomic number 2, this can also be written as:
  • The alpha particle also has charge +2, but the charge is usually not written in nuclear equations, which describe nuclear reactions without considering the electrons.
  • Alpha particles have a typical kinetic energy of 5 MeV (approximately 0.13 percent of their total energy, i.e., 110 TJ/kg) and a speed of 15,000 km/s.

• Constant Angular Acceleration

  • Simply by using our intuition, we can begin to see the interrelatedness of rotational quantities like θ (angle of rotation), ω (angular velocity) and α (angular acceleration).
  • Let us start by finding an equation relating ω, α, and t.
  • As in linear kinematics where we assumed a is constant, here we assume that angular acceleration α is a constant, and can use the relation: $a=r\alpha $ Where r - radius of curve.Similarly, we have the following relationships between linear and angular values: $v=r\omega \\x=r\theta $
  • The equations given above can be used to solve any rotational or translational kinematics problem in which a and α are constant. shows the relationship between some of the quantities discussed in this atom.

• Dependence of Resistance on Temperature

  • where ρ0 is the original resistivity and α is the temperature coefficient of resistivity.
  • For larger temperature changes, α may vary, or a nonlinear equation may be needed to find ρ.
  • Note that α is positive for metals, meaning their resistivity increases with temperature.
  • Manganin (made of copper, manganese and nickel), for example, has α close to zero, so its resistivity varies only slightly with temperature.
  • Note also that α is negative for semiconductors, meaning that their resistivity decreases with increasing temperature.

• Glancing Collisions

  • The angles between the body and the surface normal areindicated as α and β.
  • The angles between the body and the surface are 90 - α and 90 - β.

• Constant Velocity Produces a Straight-Line

  • There are many cases where a particle may experience no net force.
  • Or there could be two or more forces on the particle that are balanced such that the net force is zero.
  • If the net force on a particle is zero, then the acceleration is necessarily zero from Newton's second law: F=ma.
  • In this case a charged particle can continue with straight-line motion even in a strong magnetic field.
  • Identify conditions required for the particle to move in a straight line in the magnetic field

• The Physical Pendulum

  • where α is the angular acceleration, τ is the torque, and I is the moment of inertia.

• Problem-Solving Techniques

  • We are given the number of revolutions θ, the radius of the wheels r, and the angular acceleration α.