Chapter 19, Problem 19.4P

(a)

Interpretation Introduction

Interpretation:

Number of lines per cm has to be calculated.

Concept Introduction:

Principle behind diffraction in reflection grating can be stated with the expression as follows:

  $n\lambda =d\left(\sin \theta +\sin \varphi \right)$

Formula to compute number of lines per cm is as follows:

  $\text{Number of lines/cm}=\frac{1}{d\left(\text{lines/m}\right)}\left(\frac{1\text{ m}}{100\text{ cm}}\right)$

Here,

$d$ denotes repeat distance between closely spaced lines.

$n$ denotes order of diffraction.

$\theta$ denotes angle made by emergent line.

$\varphi$ denotes angle made by incident line.

(b)

Interpretation Introduction

Interpretation:

Number of lines per cm when wavenumber is $1000{\text{ cm}}^{-1}$ has to be calculated.

Concept Introduction:

Refer to part (a).