What is the coherence length and coherence time of the filtered light?

[warfreak131]

Homework Statement

A filter is used to obtain approximately monochromatic light from a white sources. If the pass band of the filter is 10 nm, what is the coherence length and coherence time of the filtered light? The mean wavelength is 600 nm.

Homework Equations

$$c\tau_{0}=l_{c}$$
$$<\tau_{0}>=\frac{1}{\Delta\nu}$$
$$l_{c}=\frac{c}{\Delta\nu}=\frac{\lambda^{2}}{\Delta\lambda}$$

The Attempt at a Solution

The problem gives me the wavelengths, so I would star by using the third equation. However, I don't understand the book's description of D lambda, the spectral width, and I'm not sure which wavelength to use, 600 nm or 10 nm,

 

[grey_earl]

That's not advanced physics. Still, I think that $$\lambda = 600 \tex{ nm}$$, and $$\Delta\lambda = 10 \tex{ nm}$$.

 

[warfreak131]

o, okay, thanks a lot