Electromagnetic waves spectrum Electromagnetic waves, spectrum

Electromagnetic waves waves, spectrum
Oct. 2012
Biophysics 1 st semester
József Orbán
University of Pécs, Department of Biophysics

Light g – electromagnetic g radiation
photon (quantum of radiation energy) : E = h f
Dual nature of light:
Electromagnetic wave Particle (photon)
(propagation)
Maxwell
• Diffraction
• Interference
• Polarisation
(reaction)
Einstein
A b s o r p t i o n
R e f l e c t i o n
• Photoelectric effect
• Compton effect

Propagation of electromagnetic wave
If = 600 nm then
If = 600 nm, then
f = 5·10 14 Hz
x
direction of
propagation

E
Propagation of electromagnetic wave
electric field
strength
vector t
x
magnetic field
strength vector
B
x
transversal
wave
T: period time (in time)
λ: wavelength (in space)
c = f
The electric- and the magnetic field strength vectors are
perpendicular to each other and to the direction of
propagation, ti as well!
ll!
x

Linearly y (plane) (p ) polarised p light g
If the electric field’s field s strength vector
oscillates in only one plane all along the
propagation then the wave is called
li linearly l or plane l polarised. l i d
If it is true in each point of space in a light
beam, then the beam is polarised, as well.
http://esr.elte.hu/~noemi/labor/cd/demo0.html
Animations show a
vertically polarised
electromagnetic wave (it’s
electric field’s field s oscillation) oscillation).
View from the perpendicular plane:

These animations show a horizontally polarised wave wave.
Linearly (plane) polarised.
Vi View ffrom the h perpendicular di l plane l
http://esr.elte.hu/~noemi/labor/cd/demo0.html

Total spectra p of electromagnetic g radiations
Energy, frequency (E=hf Wavelength (=1/f)
Gamma
X-ray (Röntgen)
Visible range: light
E = hf
c = f

name of
the range

Electronic energy gy levels of atoms
Bohr- and quantummechanic atommodel
Electrons have quantised (defined) energy→ energy levels!
energy (level) energy difference
Figures are only for demonstration!

Spectrum p
Spectrum:
• (light) ( g ) intensityy or analogous g quantity q y -
plotted against
• wavelength or frequency frequency.
CLASSIFICATION OF SPECTRA
Source:
Types:
• absorption ( atoms )
• line ( atoms )
• emission ( production p ) • band ( molecules )
• continuous ( any material at
high temperature: black body
radiation )

Continuous Continuous, emission
Line, emission
Continuous, emission
Line, emission
Types of spectrum
I
See: continuous emission radiation radiation, black body body, Planck Planck, Stefan Stefan-Boltzman
Boltzman
Source of images: http://csep10.phys.utk.edu/astr162/lect/light/absorption.html

absorption
Continuous, emission
Line, emission
Line Line, absorption
Types of spectrum
I
See: continuous emission radiation radiation, black body body, Planck Planck, Stefan Stefan-Boltzman
Boltzman
Source of images: http://csep10.phys.utk.edu/astr162/lect/light/absorption.html

S p e c t r a
Line type emission spectra of different atoms:

Band type yp (absorption) ( p ) spectrum p
Absorpption
2,5
2,0
1,5
1,0
0,5
00 0,0
of ACTIN molecule
How can you explain the shape?
The line spectra of atoms and
band spectra of molecules are
characteristic!
(depends on their chemical
constitution) tit ti )
actin
260 270 280 290 300 310 320
Wavelength (nm)

Absorption p of proteins p - aminoacids
There are 3 aminoacids that
absorbs in UV UV.
(Measuring the absorption spectra
of protein solution solution, the
concentration can be determined.)
Exttinctionn
coeefficientt
wavelength g

our SUN

Mitosis of Rat kangoroo kidney epithelial cell
DNS Mi Microtubuli t b li Mit Mitochondria h d i
forrás: http://micro.magnet.fsu.edu/cells/fluorescencemitosis/index.html3