Calculating Spectral Band Width for Green and Sodium Light

[Anabelle37]

Homework Statement

I'm trying to write up my physics lab but i don't know how to calculate the spectral band width.

Homework Equations

The Attempt at a Solution

I measured a coherence length for green light (546.1nm) to be 0.122mm. How do I calculate band width from this information that I measured?? Also I can't find the theoretical values for the spectral width for green light and sodium light. Does anyone know these values or know where to find them?

Thanks

 

[Anabelle37]

NOTE the 546.1nm stated is the wavelength of green light.

 

[zzzoak]

The coherence length L_{cog} and time cogerence t_{cog}
and band width \Delta f_ are related

L_{cog}=c {\;} t_{cog}=k \frac{c}{\Delta f}

where k depends on the shape of spectrum.