EMR Ranking and Light-Matter Interactions

Electromagnetic Radiation Ranking and Equations

• Fundamental Equations:

  • Energy of a photon in terms of frequency:         $E = h\nu$

  • Frequency of light in terms of wavelength and the speed of light:         $\nu = \frac{c}{\tau}$

  • Energy of a photon in terms of wavelength:         $E = \frac{hc}{\tau}$

• Functional Relationships Between Variables:

  • Energy ($E$) and Frequency ($\nu$): The frequency of a photon is directly proportional to its energy ($E \nu$). Higher frequency photons carry greater energy.

  • Frequency ($\nu$) and Wavelength ($\tau$): The frequency of a photon is inversely proportional to its wavelength ($\nu \frac{1}{\tau}$). As wavelength increases, frequency decreases.

  • Energy ($E$) and Wavelength ($\tau$): Energy is inversely proportional to wavelength ($E \frac{1}{\tau}$). Longer wavelengths correspond to lower energy.

• Specific Wavelength Regions:

  • Visible Light: Operates within the range of 300\nm to 800\nm.

  • Infrared Light (IR): Located at slightly longer wavelengths than visible light, spanning from 800\nm to 1400\nm.

  • Microwaves: Located in the $\nu\text{-wave}$ region.

• Electromagnetic Radiation Spectrum Ranking:

  • Order of Wavelengths (from longest wavelength to shortest wavelength):         $RF\text{ (radio)} > \nu\text{-wave} > IR > vis > UV > X\text{-rays} > \tau\text{-rays}$

  • Trend: Moving from radio waves ($RF$) to gamma rays ($ au ext{-rays}$), wavelength decreases while energy ($E$) and frequency ($\nu$) increase.

Interactions Between Light and Matter

• Radio Waves ($RF$):

  • Molecular/Atomic Interaction: Causes atomic nuclei to spin.

  • Conditions and Applications: Performed within a strong magnetic field. This mechanism is the operational principle behind Magnetic Resonance Imaging (MRI).

• Microwaves ($ u ext{-wave}$):

  • Molecular/Atomic Interaction: Causes electrons to spin and causes molecules to rotate.

  • Applications: Molecular rotation applied to water ($H_2O$) creates kinetic energy, which generates thermal energy to heat food.

• Infrared Radiation ($IR$):

  • Molecular/Atomic Interaction: Causes molecules to vibrate.

  • Applications: The characteristic vibration of $OH$ groups in alcohol is measured in a person's breath to determine blood alcohol concentration.

• Visible Light ($vis$):

  • Molecular/Atomic Interaction: Causes valence electrons to be excited to higher energy levels.

  • Perception: Corresponds to the visible colors seen by the human eye.

• Ultraviolet Light ($UV$):

  • Molecular/Atomic Interaction: Causes valence electrons to be excited to higher energy levels (shared mechanism with visible light).

  • Effects: High energy causes physiological damage, resulting in sunburns on human skin.

• X-Rays:

  • Molecular/Atomic Interaction: Causes inner-shell electrons to become excited.

  • Applications: Utilized to produce diagnostic X-ray images of internal body structures.

• Gamma Rays ($ au ext{-rays}$):

  • Molecular/Atomic Interaction: Possesses extreme energy strong enough to cause the atomic nucleus to fall apart.