Science

• An electromagnetic wave is not a longitudinal wave
• Electromagnetic waves carry energy
• Electromagnetic waves can travel in empty space
• Sound waves are not electromagnetic waves
• Different colors of light do not have the same amount of energy
• Electricity and magnetism can be static, but changing magnetic field will induce an electric field and vice versa
• Electromagnetic waves are formed when an electric field comes in contact with a magnetic field
• Electric and magnetic fields of an electromagnetic wave are perpendicular to each other
• Electromagnetic waves do not carry energy by causing matter to vibrate, it is the electric and magnetic fields that vibrate
• Light is a form of electromagnetic wave
• Electromagnetic waves travel in a vacuum at a speed of 3x10^8 m/s, denoted as c, the speed of light
• The speed of light is the ultimate speed limit
• Properties of electromagnetic waves:

  • They do not require any material or medium for propagation
  • They are produced by accelerated or oscillating charge
  • EM waves travel in a vacuum at the speed of 3x10^8 m/s
• Electromagnetic waves play an important role in life by carrying energy from one place to another without requiring a medium for propagation
• The history of electromagnetic wave theory begins with ancient measures to understand atmospheric electricity, particularly lightning
• Electricity and magnetism were related, and their theories were unified in the 19th century
• Scientists who contributed to the formulation of EM Theory:

  • Hans Christian Oersted discovered that an electric current can deflect a magnetized compass needle
  • Andre-Marie Ampere formulated Ampere's Law of Electromagnetism
  • Michael Faraday discovered electromagnetic induction
  • James Clerk Maxwell developed a scientific theory to explain electromagnetic waves
  • Heinrich Hertz discovered radio waves and verified Maxwell's EM theory
• Basic principles of EM Theory:

  • Many natural phenomena exhibit wave-like behaviors, requiring a medium to propagate
  • Light can be described as a wave of changing electric and magnetic fields that propagate outward without requiring a medium
  • Electromagnetic waves propagate at 3x10^8 m/s through a vacuum
  • Electromagnetic waves are transverse waves with changing electric and magnetic fields oscillating perpendicular to each other and to the direction of propagation
  • When the oscillating charge accelerates, the moving charge's electric fields change
• An inverse relationship means as one increases, the other decreases
• As frequencies increase on the EM spectrum, wavelengths decrease
• Radio waves have shorter wavelengths than ultraviolet rays
• All forms of EM waves can have varying speeds in a vacuum
• Gamma rays have the highest frequency and therefore contain photons with lowest energies
• Electromagnetic waves travel at the speed of 300,000,000 m/s
• Radio waves and visible light have varying wavelengths and frequencies
• Electromagnetic waves are described by their physical wave features: amplitude, wavelength, and frequency
• Direct proportion is a relationship where both quantities have the same or equal value
• Inverse proportion is a relationship where two quantities have opposite or do not have the same value
• Higher frequency corresponds to shorter wavelength, while lower frequency corresponds to longer wavelength
• The electromagnetic waves are often arranged in the order of wavelength and frequency in what is known as the electromagnetic spectrum
• As frequency increases, wavelength decreases
• The electromagnetic spectrum displays waves in the following order: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays
• There is no exact dividing region between the different types of electromagnetic waves
• Different types of electromagnetic waves are defined by the amount of energy carried by their photons
• Photons are bundles of wave energy
• Gamma rays carry photons of high energies, while radio waves carry photons with the lowest energies
• The higher the frequency, the higher the photon’s energy
• Sample Problem: What is the wavelength of an EM wave with a frequency of 3.0x10^15 Hz?
• Sample Problem: A certain microwave has a wavelength of 3.2x10^-3 meters. Calculate the frequency of this microwave
• Sample Problem: Calculate the energy possessed by an x-ray whose frequency is 3.0x10^17 Hertz