Understanding the Electromagnetic Spectrum and Relativity

The Electromagnetic Spectrum

In a vacuum, electromagnetic waves move at the same speed and differ from each other by their frequency. They are classified by the frequency of the electromagnetic spectrum.

Frequency Classifications

• Radio Waves: Thousands of Hertz (kHz) are considered very low frequency.
• AM Radio: One million Hertz (MHz).
• TV Band: Very high frequency (VHF) waves begin at about 50 MHz.
• FM Radio: Operates between 88-108 MHz.
• UHF: Ultra-high frequency waves.
• Microwaves and Infrared: Often referred to as heat waves.

Visible Light and Higher Frequencies

Visible light constitutes less than a millionth of 1% of the electromagnetic spectrum. The minimum frequency visible to the human eye is red, while the maximum frequency is nearly twice that of red, appearing as violet. Higher frequencies include ultraviolet radiation.

Energy Distribution

The electromagnetic spectrum represents the energy distribution of electromagnetic waves, categorized by the radiation emitted (emission spectrum) or absorbed (absorption spectrum) by a substance.

Modern Physics and Relativity

By 1900, several physical phenomena could not be explained by classical physics. Newtonian concepts regarding mass, length, and time were found to be inadequate. These unexplained phenomena, such as the light produced by electric sparks in gas, led to new ways of understanding the universe.

In 1905, Albert Einstein published his first work on relativity, followed by further research in 1916, laying the foundation for universal physics. These principles set parameters for modern electronics, chemical analysis, space travel, and nuclear energy.

Cosmology and the Expanding Universe

Approximately 15 billion years ago, the universe existed as a small mass where protons, neutrons, neutrinos, and antineutrinos collided to create matter. It is widely believed that the universe is expanding; Edwin Hubble observed that galaxies are receding from the Milky Way. The Sun is estimated to be 4.65 billion years old.

Hubble's Law

Proposed in 1930, this law states that galaxies are receding in proportion to their distance from each other. According to the Big Bang model, the universe is finite.

Relativity Principles

• Galilean Relativity: Describes inertial systems and Galilean variance.
• Inertial Systems: Systems that satisfy Newton's laws of motion.
• Galilean Variance: Time and length are affected by the exchange of inertial systems.
• Einstein's Theory (1905):
  1. In all Galilean reference systems, there is no speed limit for bodies.
  2. The velocity of light is constant regardless of the observer's reference frame.