© 2002 J.Paul
Robinson, Purdue University BMS 631- Flow Cytometry lecture002.ppt

Page 20

Terms

•**Side
scatter, forward angle scatter, cell volume, ****coulter volume****:
**

•Understand light scattering
concepts; intrinsic and extrinsic parameters

•**Photometry:
**

•**Light** - what is it - wavelengths we can
see 400-750 nm, most sensitive around 550 nm. Below 400 nm essentially measuring
radiant energy. Joules (energy) **radiant flux** (energy per unit time) is measured in watts (1 watt=1
joule/second).

•**Steradian** (sphere radius r has surface area
of 4 pr2; one steradian is defined as that solid angle which intercepts an
area equal to r2 on the surface.

•**Mole** - contains Avogadro's number of
molecules (6.02 x 1023) and contains a mass in grams = molecular weight. Photons - light particles - waves - **Photons** are particles which have no rest mass - pure
electromagnetic energy - these are absorbed and emitted by atoms and molecules as
they gain or release energy. This process is **quantized**, is a discrete process involving
photons of the same energy for a given molecule or atom. The sum total of
this energy gain or loss is **electromagnetic ****radiation** propagating at the speed of light
(3 x 108 m/s). The energy
(joules) of a photon is

•E=hn and E=hn/l [n-frequency, l-wavelength, h-Planck's constant 6.63 x
10-34 joule-seconds]

•**Energy** - higher at short wavelengths -
lower at longer wavelengths.