electromagnetic radiation

• many types, each with different wavelengths and frequencies

• frequency (ν): the number of waves that pass a fixed point in a second

  • measured in Hz (waves/second, cycle/second, 1/s, s-1)

• wavelength (λ): inversely related to frequency

  • waves are measured in meters (m) or nanometers (1m = 109 nm); nm are usually used in the visible region

  • measured from the peak of one wave to the peak of the next, or the trough of one wave to the trough of the next

• light in the visible range (colors) is the only type of electromagnetic radiation that the human eye can detect

light

• light is composed of electromagnetic radiation

  • has wave-like properties and is characterized by wavelength, frequency, and speed

  • dependent on electronic structure (how the formation of electrons in an atom is) and electromagnetic radiation

• electromagnetic radiation travels in waves that have electric fields and magnetic fields perpendicular to each other

• the speed of light

  • variable =c, constant in a vacuum

    • c = 3.00 x 108 meters per second

    • c = λν

• divided into spectra which dictate different properties, namely whether the human eye can detect its presence and appearance in color

matter vs. energy

• in the early twentieth century, matter and energy were viewed as fundamentally distinct

  • matter was composed of particles

  • energy was composed of waves

  • this later developed into the notion that energy existed in particles

• Planck then developed the theory that energy is quantized

  • particles of energy are called quanta (the single form of which is quantum)

  • relationship between energy and frequency: E=Hν

  • energy can behave as both waves and particles

  • Planck constant: constant h; 6.62 x 10^-34 joule-seconds

• frequency (ν) is the bridge between the two units

properties of energy

• quantized energy (detailed further in next note) is measured by Planck’s constant, units are quantum and photons

• energy of photon = Planck constant x frequency

properties of matter

• contain matter waves, or the wave characteristics present in material particles

• momentum describes the quantity mv (mass x velocity) of any object

• Heisenberg’s uncertainty principle posits that it is impossible for people to know simultaneously the exact momentum of an electron and its exact location in space

  • these cannot be measured at the same time, but estimations can be made to approximate one or the other