# (a) Interpretation: For an angle of incidence of 45 0 , the effective penetration depth of the evanescent wave should be determined. Penetration depth if the angle changed to 60 0 should be determined. Concept introduction: The effective penetration depth can be calculated as follows: d p = λ c 2 π [ sin 2 θ − ( n s / n c ) 2 ] 1 / 2 Here, d p − effective penetration depth λ c − Wavelength of the beam θ − incident angle n s − refractive index of the sample n c − refractive index of the crystal

### Principles of Instrumental Analysis

7th Edition
Douglas A. Skoog + 2 others
Publisher: Cengage Learning
ISBN: 9781305577213

### Principles of Instrumental Analysis

7th Edition
Douglas A. Skoog + 2 others
Publisher: Cengage Learning
ISBN: 9781305577213

#### Solutions

Chapter 17, Problem 17.13QAP
Interpretation Introduction

## (a)Interpretation:For an angle of incidence of 450, the effective penetration depth of the evanescent wave should be determined. Penetration depth if the angle changed to 600 should be determined.Concept introduction:The effective penetration depth can be calculated as follows:dp=λc2π[sin2θ−(ns/nc)2]1/2Here,dp− effective penetration depthλc− Wavelength of the beamθ− incident anglens− refractive index of the samplenc−refractive index of the crystal

Interpretation Introduction

### (b)Interpretation:The penetration depths for sample refractive indexes varying from 1.00 to 1.70 in steps of 0.10 should be determined. Penetration depth should be plotted as a function of refractive index. The refractive index for which the penetration depth becomes zero should be determined.Concept introduction:dp=λc2π[sin2θ−(ns/nc)2]1/2dp− effective penetration depthλc− Wavelength of the beamθ− incident anglens− refractive index of the samplenc−refractive index of the crystal

Interpretation Introduction

### (c)Interpretation:For a sample with a refractive index 1.37 at 2000 cm-1 and incident angle of 450, the penetration depth versus the ATR crystal refractive index should be plotted.Concept introduction:The effective penetration depth can be calculated as follows:dp=λc2π[sin2θ−(ns/nc)2]1/2Here,dp− effective penetration depthλc− Wavelength of the beamθ− incident anglens− refractive index of the samplenc−refractive index of the crystal

Interpretation Introduction

### (d)Interpretation:The effective penetration depth at 3000 cm-1, 2000 cm-1 and 2000 cm-1 should be determined.Concept introduction:The effective penetration depth can be calculated as follows:dp=λc2π[sin2θ−(ns/nc)2]1/2Here,dp− effective penetration depthλc− Wavelength of the beamθ− incident anglens− refractive index of the samplenc−refractive index of the crystal

Interpretation Introduction

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