Recent content by nicp

Once upon a time, the intensity of a luminous source was measured by comparing it with a reference source using measuring sistems called photometers (Bunsen's one is the most famous). The primary reference source was 1 cm^2 of platinum brought at its melting temperature, which was defined to...

In order for me to try to answer at your questions plese explain me how it works laser anemometry. I suppose that you use reflection of light by the air and you make reflected and original beam interfere with each other. Please explain me into more details. And how do you measure the frequency...

I tried to perform the calculation of the spectrum. I got the spectrum dP/df (power emitted each frequency unit): dP/df = Pt >< dv/df >< fr(v) Pt is the total power emitted by the gas, fr(v) is the Maxwell distribution regarding the radial component of speed (component in observer's...

Flux is an amount of light. We can say a light beam has a certain flux, through a window pass a certain flux, on a given surface arrive a certain flux, etc. Intensity is a characteristic of a source: a source which emits a certain flux in unit solid angle is said to have a certain intensity.

Relation 1) is correct. The total flux emitted by a source is 4pi times the intensity of that source. So a source of intensity 1 cd emits total 4pi lumen, 1 lm for each solid angle unit. In a certian way we could write 1 cd = 4pi lm, but it's not completely correct because cd and lm are not...

As you have said, flux is the total amount of light emitted by a source per second. Light is energy, so flux is power, and so the best way to measure flux is using watts. Lumen is an other unit, which corresponds to a certain number of watts depending on wavelength. For instance at 550 nm...