# Homework Help: Luminesence of Sources

1. Dec 6, 2009

### Diemo

1. The problem statement, all variables and given/known data
Estimate the radiance (in W cm-2 sr-1) of the following sources:
(1) A He-Ne Laser, with a beam area of 1mm2, output power of 1 mW and a beam divergence of 1mrad.
(2) a 100 Watt tungsten lamp at a distance 1 m from the lamp.

2. Relevant equations

Well, what I have is that the luminescence is L = Phi /(Omega(A)(Cos(Theta))
Where Phi is your power emitted
A is the area of source
Omega is solidangle subtended
Theta is your angle between surface and specified direction

We also have that Omega is A/r2

3. The attempt at a solution
So, in this case we have
P=1*10-3 W\(1*10-3m2*1*10-3radians)

Except that you want it is steradians, not radians, so pretty sure what I am doing there is wrong.. How would you do this?

For the second one, how do you work out what Omega is? Or what area you should be considering?

Thanks in advance.

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