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

Page 19

Light and Matter

•Energy

–joules, radiant flux (energy/unit time)

–watts (1 watt=1
joule/second)

•Angles

–steradians -
sphere radius *r* - circumference is 2p*r*2; the angle that intercepts
an arc r along the circumference is defined as 1 radian. (57.3 degrees) a sphere of radius *r* has a surface
area of 4p*r*2. One steradian is defined as the
solid angle which intercepts as area equal; to *r*2 on the sphere surface

3rd Ed - Shapiro p 75