Chapter 2

Question 1

Characteristics of source of radiation

Answer 1

1. Generate stable beam of radiation.

2. Has sufficient power.

Question 2

Function of spectrometer

Answer 2

Provides information about the intensity of radiation in wavelength

Question 3

5 basic optical intstrument components

Answer 3

1. Source
2. Sample Container
3. Wavelength Selector
4. Detector
5. Signal Processor & Readout

Question 4

The correct order of Absorption Optical Instruments design

Answer 4

Source -> Wavelength selector -> Sample -> Detector -> Signal processor & readout

Question 5

The correct order of Emission Optical Instruments design

Answer 5

Source -> Wavelength selector -> Detector -> Signal processor & readout

Question 6

Characteristics of Continuum Sources

Answer 6

1. Emit radiation over a broad wavelength range
2. The intensity of radiation changes slowly in wavelength
3. Commonly used in UV, Visible and IR instruments

Question 7

Examples of Continuum Sources

Answer 7

1. Deuterium lamp (UV)
2. Tungsten filament lamp (visible)
3. Glowing inert solids (IR)

Question 8

Characteristics of Line Sources

Answer 8

1. Emit a limited number lines of radiation at specific wavelengths
2. Used in Atomic Absorption Spectroscopy & Molecular Fluorescence Spectroscopy
3. Provide UV & Visible radiation in EM spectrum region

Question 9

Examples of Line sources

Answer 9

1. Mercury vapor lamp (UV)
2. Sodium vapor lamp (Visible)
3. Hollow Cathode lamp (Atomic Absorption)

Question 10

Characteristics of Laser Sources

Answer 10

1. Light Amplification by Stimulated Emission of Radiation
2. Used in Molecular Absorption Spectroscopy & Raman Spectroscopy
3. Provide high intensity of radiation & monochromatic beam

Question 11

Characteristics of Sample Containers

Answer 11

1. Used in all spectroscopic studies except emission spectroscopy
2. Called as cuvettes
3. Must have transparents windows in the spectral region

Question 12

Types of sample containers (cuvettes)

Answer 12

1. Quartz (UV, below 350 nm)
2. Silicate glass (UV, 350-2000 nm)
3. Plastic (Visible region)

Question 13

Function of Wavelength selectors

Answer 13

To isolate the desired wavelength from the band of interest

Question 14

Two types of wavelength selectors

Answer 14

1. Filters

2. Monochromators

Question 15

Two types of UV

Answer 15

1. Single beam

2. Double beam

Question 16

The cause of electronic transition

Answer 16

Interaction between ultraviolet and visible radiation with matter

Question 17

3 types of electronic transitions

Answer 17

1. organic compounds (sigma, pi, n)
2. inorganic compounds (d, f electrons)
   3 charge transfer electrons

Question 18

Characteristics of Sigma electron

Answer 18

1. single bond (saturated hydrocarbons)
2. doesnt absorb UV radiation
   - bc it requires high energy to excite sigma electrons
3. mostly used as transparent solvents

Question 19

Characteristics of Pi electron

Answer 19

1. double & triple bonds (unsaturated hydrocarbons)
2. alkenes, alkynes, conjugated olefins
3. absorb UV or Visible radiation
   - the electrons are excited easily

Question 20

Characteristics of n electrons

Answer 20

1. lone pair
   - not involved in formation bonds
2. organic compounds containing oxygen, halogen, sulfur
3. Absorb UV or Visible radiation

Question 21

definition of chromophores

Answer 21

Unsaturated functional groups that absorb in UV or Visible region

Question 22

Molecular orbital theories

Answer 22

1. formed when bonding (sigma & pi) and antibonding (sigma* & pi*) interact
2. stable bonding molecular orbital = lower energy
3. less stable antibonding molecular orbital = higher energy