Electromagnetic Radiation

Light

  • a changing magnetic fields induces a changing electric field → faradays law

    • they go hand in hand

  • this changing electric field will induce a changing magnetic field (in accordance with maxwells counterpart to fardays law)

  • these vibrating magnetic and electric fields regenerate one another which makes an electromagnetic wave

    • this eminates from the vibrating charge

      • strength of the electromagnetic field depends on speed of emanation.

  • oscillation of charges makes an electromagnetic wave

Understanding electromagnetic radiation

  • it is the transfer of energy because of oscillating electic and magnetic fields inducing each other

  • travel at the speed of light in a vacuum

    • 3× 10^8

  • electric and magnetic fields are vectors at 90 to each other

  • electromagnetic waves show all the properties of waves that others do

Frequency and Wavelength equation

c = f(wavelength)

c = speed of light

f = frequency

wavelength

Electromagnetic spectrum

  • classification of electromagnetic waves according to frequency

  • visible light between 7 × 10-7 and 3.8 ×10-7

  • frequency and wavelength list light in the opposite order

    • e.g radio has smallest frequency but highest wavelength

Annoying chart thing summary

name

produced

uses

danger

Radio

free electrons

oscillating in

matter

comms

cancer

Micro

free electrons

oscillating in

matter

cooking

dont stand

close

Infared

vibrational energy

changes of

molecules

remotes

overuse

Visible

energy changes

in outer shell

of an atom

seeing

damage

retina

Ultraviolet

energy changes

in outer shell

of an atom

photography

cancer

Xray

energy changes

of inner orbital

electrons in atom/

fast electrons

slowing down

medical

cell damage

Gamma

nuclei changes in

radioactive substances

kills cancer

cell damage

The particle nature of electromagnetic radation

  • photoelectric effect → proves that EM radaition can behave as beam of prticles

    • called photons → have energy yet are massless

    • energy corresponds to the frequency and wavelength as seen in plancks law

  • plancks law

    E = hf = hc/wavelength

    • h = plancks constant

    • allows us to calculate energy of a photon at any wavelength

    • E and f have a direct relationship, ammended by plancks law

Wave particle duality

  • electromagnetic radiation (which is a type of light essentially, or is light)

    • some aspects explained using wave model, other particle model (double slit experiment proved that light acts both as particles and waves)

Definitions (that i know off)

electromagnetic radiation - the transfer of energy due to the mutual induction of oscillating electric and magnetic fields

Textbook Practise/Knowledge

  • electromagnetic waves are formed from a charge (electron) oscillating rapidly. Moves away at 90 from direction which charge is oscillating.

  • the charge changes (electron) its position and time which in turn creates a changing electric and magnetic field. These changing fields induce other magnetic and electric fields in their vicinity → disturbance travels outward

  • electromagnetic waves are tranverse

  • electric field is parralel to motion of electron

  • magnetic field is perpendicular

  • electromagnetic wave induces current by induction

  • tranverse waves because the magnetic and electric fields are at 90 to each other