• wavelength vs. frequency• photon• kV vs. keV• ionizing radiation• spectrum
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Visible light
• Electromagnetic (EM) radiation with wavelengths between 400 and 700 nm• Each wavelength corresponds to a different color
– Monochromatic vs. polychromatic colors– Monoenergetic vs. polyenergetic energy– Spectrum
• Spectroscopy
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Frequency is equivalent to an energy
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• Waves– The speed of EM radiation is constant– 𝑐 𝜆𝜈 (m Hz = m cycles/s = m s‐1)– e.g., What is the frequency (𝜈) of blue light with a wavelength (𝜆) of 400 nm?
• 𝜈 / /
7.5 10 s 7.5 10 Hz
• Particles– Photons: the discrete (particle‐like) packets (or quanta) of EM energy
– 𝐸 ℎ𝜈• ℎ = Plancks constant = 6.626 10 J s = 4.136 10 keV s
– 𝐸 keV .
or 𝐸 eV .
X‐ray spectrum as a function of wavelength
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frequency (Hz) or energy (eV or keV)
X‐ray spectrum as a function of energy
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Wrap‐up
• wavelength vs. frequency• photon• kV vs. keV• ionizing radiation• spectrum
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