Electromagnetic Spectrum

The Electromagnetic Spectrum

The electromagnetic spectrum encompasses the complete continuum of electromagnetic radiation, characterized by wavelength, frequency, and photon energy levels.

Diagram of the electromagnetic spectrum showing penetration of Earth's atmosphere, radiation type, wavelength, wavelength scale, and frequency

Diagram showing the electromagnetic spectrum and visible spectrum with corresponding wavelengths in nanometres and energy in electron volts

  • Radio Waves:

    • Wavelength: 103 m10^3\,m (5,000,000,000 nanometres5,000,000,000\,\text{nanometres})
    • Frequency: 104 Hz10^4\,Hz
    • Energy: 0.000000248 electron volts0.000000248\,\text{electron volts}
    • Penetrates Earth's Atmosphere: Yes (Y)
    • Approximate Scale of Wavelength: Buildings

  • Microwaves:

    • Wavelength: 10−2 m10^{-2}\,m (10,000 nanometres10,000\,\text{nanometres})
    • Frequency: 108 Hz10^8\,Hz
    • Energy: 0.124 electron volts0.124\,\text{electron volts}
    • Penetrates Earth's Atmosphere: No (N)
    • Approximate Scale of Wavelength: Humans

  • Infrared:

    • Wavelength: 10−5 m10^{-5}\,m (500 nanometres500\,\text{nanometres})
    • Frequency: 1012 Hz10^{12}\,Hz
    • Energy: 2.48 electron volts2.48\,\text{electron volts}
    • Penetrates Earth's Atmosphere: Partial / Yes (Y)
    • Approximate Scale of Wavelength: Butterflies to Needle Point

  • Visible Spectrum:

    • Wavelength: 0.5×10−6 m0.5 \times 10^{-6}\,m (250 nanometres250\,\text{nanometres} scale mark)
    • Frequency: 1015 Hz10^{15}\,Hz
    • Penetrates Earth's Atmosphere: Yes (Y)
    • Approximate Scale of Wavelength: Protozoans

  • Ultraviolet:

    • Wavelength: 10−8 m10^{-8}\,m (0.5 nanometres0.5\,\text{nanometres})
    • Frequency: 1016 Hz10^{16}\,Hz
    • Energy: 4.96 electron volts4.96\,\text{electron volts}
    • Penetrates Earth's Atmosphere: No (N)
    • Approximate Scale of Wavelength: Molecules

  • X-Rays:

    • Wavelength: 10−10 m10^{-10}\,m
    • Frequency: 1018 Hz10^{18}\,Hz
    • Energy: 2480 electron volts2480\,\text{electron volts}
    • Penetrates Earth's Atmosphere: No (N)
    • Approximate Scale of Wavelength: Atoms

  • Gamma Rays:

    • Wavelength: 10−12 m10^{-12}\,m (0.0005 nanometres0.0005\,\text{nanometres})
    • Frequency: 1020 Hz10^{20}\,Hz
    • Energy: 2,480,000 electron volts2,480,000\,\text{electron volts}
    • Penetrates Earth's Atmosphere: No (N)
    • Approximate Scale of Wavelength: Atomic Nuclei

History of Nuclear Medicine

The development of nuclear medicine involves key historical milestones, discoveries, and technological innovations:

  • 1896: Henri Becqurel discovered radioactivity.
  • 1898: Marie Curie discovered radium and coined the term radiation.
  • 1927: The first tracer was injected into a human.
  • 1930s: The first cyclotron was created, allowing for the production of artificial elements.
  • 1940s: As a part of the Manhattan Project, nuclear reactors were producing enough isotopes for wide scale use.
  • 1951: Benedict Cassen created the rectilinear scanner.
  • 1958: Hal Anger created what is the framework on which all modern gamma cameras are built.
  • 1970s: Algorithms were created to digitally recreate images in computers.

Overview of Radioactive Decay

Radioactive decay represents structural reorganizations within unstable atomic nuclei:

  • Definition of Nuclear Decay: Nuclear decay is a change made by the nucleus of an atom to become more stable.
  • Parent Nucleus: The more unstable initial nucleus that undergoes nuclear change.
  • Daughter Nucleus: The product resulting from the nuclear change of the parent nucleus.
  • Spontaneous Nature: The process of radioactive decay is spontaneous and cannot be predicted.
  • Mass-to-Energy Conversion:
    • Radioactive decay facilitates the conversion from mass to energy.
    • Transition Energy (QQ): The exact amount of energy converted during radioactive decay.

Chemistry and Radioactivity

The separation of nuclear structure from electronic interactions dictates how radioactive isotopes behave in chemical systems:

  • Definition of Chemistry: Chemistry is the study of how electrons from one atom interact with electrons of another atom.
  • Nuclear Independence of Chemical Properties:
    • Radioactive decay originates exclusively in the nucleus of an atom.
    • Because it originates in the nucleus, radioactive decay has little to no effect on the chemical properties of that atom.
  • Tracer Applications:
    • The minimal effect of nuclear decay on chemical behavior makes radionuclides an excellent tracer.
    • Isotopic Behavior Example: If stable Iodine-127 (I127I127) is replaced with radioactive Iodine-131 (131131) in a chemical equation, they do not behave differently. Their chemical interactions remain identical because electron interactions are unchanged by nuclear radioactive decay.