Photon Flux per Unit Wavelength

[QwertyXP]

Hi

How do you get a photon flux per unit wavelength curve for solar radiation? My understanding of "per unit wavelength" is that the wavelengths within a very short range are fired at a detector. The range is then gradually changed to cover higher wavelengths. The values of flux measured by the detector are divided by the size of range.

1) Is this how it works?

2) Also, how do you restrict the solar radiation to lie within a specific "range"? Wouldn't a filter only allow photons of a single wavelength, not range of wavelengths.

Thank you.

 

[mfb]

The usual way to measure a spectrum:
Use a narrow slit and a prism afterwards to split the light into a spectrum. Place a line of sensitive elements after the prism, so each pixel receives to some specific, narrow frequency range. Use some method to calibrate the whole setup (frequency and intensity).

Also, how do you restrict the solar radiation to lie within a specific "range"? Wouldn't a filter only allow photons of a single wavelength, not range of wavelengths.

Filters always have some frequency range. This can be something like "400-800nm", or "534.4-534.5nm", or whatever, depending on the requirements.