The magnitude of the magnetic field produced depends

The magnitude of the magnetic field produced depends on both the vibration rate of the
electrical field and the speed at which the filed emanates from the vibrating charge
 Higher the speed, greater the magnetic field
 Energy is equally divided between electrical and magnetic that are perpendicular
 All EMR have the same velocity –3x10^8 m/sec
 History: radiated energy could NOT be emited with a continuous spectrum of energies,
but was emitted with a specific quantum of energy
 Each emitted bundle of energy had a v specific quantum of energy associated with it
 Main points of photoelectric effect
- bodies emit radiation (energy) as an EM wave
- emission occurs as a pulse rather than as continuous event, and the pulse came to be
known as a photon
- photosn travel at the speed of light, also have freq an wavelength
- energy of photon is proportional to its freq
- radiant energy is propagated along a wave, but in a quanta of energy that behave like
particles
- photons have no mass at rest, but significant mass when moving at the speed of light
 Higher the frequency, higher the amount of energy. Hence the h constant (plank)
 Photons are quantized, tiny and massless products
 EM radiation is dualistic
 EM have wave-like properties
 EM radiation can be thought as a radiant energy transported in photons which are carried
along by a wave field
 Eventually, everyone figured out that these types of radiation (cosmic rays, x rays, radio
waves etc) are all the
same but differ in
frequency and energy
involved
 Can be seen as a spectrum

 Ionizing radiation is discussed in terms of energy
 While non-ionizing is described by wavelength
 Electromagnetic spectrum ranges from very high energy (tiny wavelength) to low
energy (very long wavelength)
 When an emission interacts with a target, it transfers some or all of its energy to the
target
 Ions cause chemical reactions in tissue, and all kinds of damage
 Bottom line – ionizing radiation causes ions to be formed in tissue and that causes
health effects.
 More than 7.4 eV
 Ionization: on the EMR scale all radiation that is above about 10 eV is ionizing, so
this included all cosmic rays, all y-rays, all x-rays and most UV rays
 On the EMR scale, all radiation that is above 10 eV is ionizing
 Neutrons, B-particles, a-particles, positrons are all energetic enough to cause
ionization as well
 When the neutral atom loses an e-, It becomes an ion – actually, an ion pair
 Ions are v reactive
 As the particle continues to transfer energy to the targe, it will continue to creat ion
pairs
 Each ion pair creation takes about 10 eV of energy
 Neutral atom: 2 p and 2 e-
 Ion: 2 p and 1 e-
 Common result from these interactions is the production of ion pairs in the material
that absorbs the energy
 Humans have about 10^12 cells – what is the most common molecule in a cell
 Cels are mostly water – so the most common effect of absorbing radiation begins with
the ionization of water
