EEPS Electromagnetic Spectrum

Introduction to Electromagnetic Radiation

  • Surrounds and bombards us

  • Invisible (cannot see, touch, or feel)

  • Odorless and tasteless; essential for life

  • Necessary for existence as we know it

The Electromagnetic Spectrum

  • Definition: The range of all types of EM radiation.

Electromagnetic Waves (EM)

  • Resemble ocean waves; transmit energy.

  • Produced by the vibration of charged particles (e.g., electrons).

  • Possess electrical and magnetic properties.

Wave Properties

  • Speed of Light: Approximately 480,000 miles/s or 1.7 billion mph.

  • Wavelength and Frequency Relationship:

    • The relationships between speed (c), frequency (f), and wavelength (λ) apply to all wave phenomena (light, sound, etc.).

Visible Spectrum

  • Plots of frequency or wavelength known as spectra.

  • Relationship between wavelength, speed, and frequency.

Historical Context

  • Colors can be separated using a prism (e.g., discovered by Roger Bacon, Isaac Newton, William Herschel).

  • Predicted by Maxwell’s equations (1861-1862) that describe electromagnetism.

  • Key figures:

    • James Clerk Maxwell: Scottish physicist

    • William Herschel: discovered infrared waves (1800)

    • Heinrich Hertz: discovered radio waves (1887)

    • Wilhelm Roentgen: discovered X-rays (1895)

    • Henri Becquerel: discovered gamma rays (1896)

Radio Waves

  • Example: Jupiter emits radio waves due to its magnetic field's interaction with solar wind.

  • Solar wind: constant stream of particles and magnetic fields from the Sun.

  • Telescopes: Very Large Array (VLA) in New Mexico; Atacama Large Millimeter Array (ALMA) in Chile.

Radio Telescope Imaging

  • ALMA: Protoplanetary disk imaging; uses false color images for intensity mapping.

  • Passive signal reception across 35-950 GHz ranges.

Weather and Air Traffic Control Radars

  • Weather radar: Used for tracking storms (ex: Hurricane Donna, 1960).

  • Air Traffic Control: Active radar emitting/receiving signals to track aircraft.

Infrared Imaging

  • Frequencies: 300 GHz – 430 THz.

  • Used for thermal imaging (e.g., human body emits infrared energy).

X-rays

  • High energy range: 30 ExaHz - 30 PetaHz.

  • Applications in medicine (e.g., examining vaper’s lungs).

Gamma Rays

  • Frequency range: YottaHz - ExaHz.

  • Sources: Emissions from black holes.

Cosmic Microwave Background

  • Relates to the history of the universe.

  • Note on radiation: All objects emit EM waves characteristic of their temperature.

Blackbody Radiation

  • Objects in thermodynamic equilibrium emit light based on their surface temperature.

  • Stars characterized by color and temperature (e.g., sunlight peaks in visible spectrum).

Visual Perception

  • Human eyes detect most intensely emitted rays from the Sun (visible light spectrum).

  • majority of the Sun's radiation is in the green-yellow range.

Atomic Structure Overview

  • Niels Bohr model of atoms outdated.

  • Modern understanding includes a nucleus with protons and neutrons, surrounded by a probability cloud of electrons.

Energy Dynamics in Atoms

  • Potential and kinetic energy converted in atoms (analogy with arrows).

  • Movement of energy between sets of energy levels, likened to bookcases' shelves.

Emission and Absorption Spectra

  • Atoms exhibit unique spectra based on energy transitions.

  • Emission spectrum: Bright lines on a dark background for hot gases.

  • Absorption spectrum: Dark lines on a continuous spectrum for cold gases.

Photon Energy Calculations

  • Energy of photons: E = hc / λ (Planck’s constant and speed of light).

  • Quantized energies for distinct elements.

Ionizing and Non-Ionizing Radiation

  • Classifications based on energy: Ionizing radiation can remove electrons from atoms (e.g. X-rays).

  • Non-ionizing radiation generally found in microwaves and visible light.

  • Health implications of ionizing radiation include DNA damage and cancer risks.

Radiation Exposure and Safety

  • Average radiation dose per person in U.S. is 6.2 mSv annually.

  • High doses lead to increased cancer risks.

  • Sources of radiation include cosmic rays, radon, and medical x-rays.

Microwaves and Safety Considerations

  • Microwave cooking retains more nutrients than conventional methods.

  • Microwaves use non-ionizing radiation, considered safe when used as directed.

Conclusion

  • Understanding of electromagnetic radiation aids in recognizing its omnipresence in daily life and its impacts.