# What is this quantity called?

1. Sep 27, 2010

### Mu naught

If you take the Flux of a light source and multiple by the area of your detector you are left with a quantity in units of only watts.

Now this is technically "power", but what is the correct term for this quantity?

2. Sep 27, 2010

### mkarger

Luminosity is a function of the amount of light output (brightness or flux) per given unit of surface area multiplied by the total surface area.

L= b*((d^2)*pi*4)

L=luminosity (watts)
b=brightness or flux ("watts/meters^2")
d=diameter of star (meters)
((d^2)*pi*4)=surface area (meters^2)

It's basically the surface area (m^2) of the sphere multiplied by the brightness per unit of area. Which finds the total output (commonly shown in the form of watts.).

Last edited: Sep 27, 2010
3. Sep 27, 2010

### Mu naught

No, because luminosity describes the total amount of energy emitted by an object.

I'm talking about multiplying the apparent brightness of an object by the area of a detector to get the total amount of energy per second falling on that detector. I believe there is a certain term for this that is not "power" but I don't know what that term is.

4. Sep 27, 2010

### mkarger

I think you're talking about "radiant flux" if you are talking about the amount per surface area unit per second observed by a detector.