© 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.