Chapter 11, Problem 11G.4P

(a)

Interpretation Introduction

Interpretation:

The coherence length of a typical light bulb and a $\text{He-Ne}$ laser with $\lambda =633\text{ nm}$ and $\Delta \lambda =2.0\text{ pm}$ has to be compared.

Concept introduction:

The laser is an abbreviation name of “Light Amplification by Stimulated Emission of Radiation”.  The laser gives light after the amplification process.  A laser beam contains a large number of photons.  The formula of coherence length is given by the expression as shown below.

    $l_{\text{c}}=\frac{{\lambda }^2}{2\Delta \lambda }$

(b)

Interpretation Introduction

Interpretation:

The condition under which coherence length becomes infinity has to be stated.

Concept introduction:

As mentioned in the concept introduction in part (a).