Chapter 6

Question 1

Spectophotometry

Answer 1

measures chemical concentration using light(electromagnetic radiation)

Question 2

Four frequency decoding devices

Answer 2

prisms, diffraction gratings, Michelson interferometer, Fabry-Perot interferometer

Question 3

Diffraction gratings

Answer 3

uses diffraction and interference to separate light into different wavelengths. more lines/mm = greater separation

Question 4

Prisms

Answer 4

separate light into its wavelengths due to a difference in refractive index

Question 5

Coherent radiation

Answer 5

Diffraction of electromagnetic energy through two slits, must be coherent such that waves of the same frequency and phase relationship to create the band pattern imaged below

Question 6

Super position Principal

Answer 6

constructive and destructive interference of electromagnetic waves that occupy the same domain

Question 7

Refractive index of a medium

Answer 7

Determines how much EMR will bend when it passes from a substance of one density to a substance f another

Question 8

Dispersion

Answer 8

When refractive endex changes with changes in wavelength or frequency

Question 9

Normal dispersion of a substance

Answer 9

Gradual change in refractive index as the frequency changes

Question 10

Anomalous dispersion

Answer 10

As frequency changes, there is a sharp change in refractive index. This is the frequency at which the analyte will absorb

Question 11

Work function of a substance

Answer 11

A CONSTANT SPECIFIC TO EACH METAL MATERIAL COATING A PHOTOTUBE THAT SPECIFIES THE MINIMUM ENERGY OF THE BINDING ELECTRON

Question 12

Photoelectric effect

Answer 12

EMR acts as both a particle(photon) and a wave

Question 13

ground state of a molecule

Answer 13

All electrons in predicted energy levels. Lowest energy state.

Question 14

electronic excitation

Answer 14

moving an electron from its ground state to a higher energy

Question 15

fluorescence

Answer 15

Photon in photon out. Light that is re-emitted will be the same (resonance fluorescence=atoms), or lower in energy (non-resonance fluorescence).

Question 16

Phosphorescence

Answer 16

When an excited molecule relaxes into a triplet state. Much longer lifespan than fluorescence.

Question 17

Transmittance

Answer 17

The portion EMR that is not absorbed, because not at the correct wavelength to meet the harmonics of the molecule.

Question 18

Absorptivity

Answer 18

The ability of a molecule to absorb light at a particular wavelength

Question 19

Absorbance

Answer 19

The amount of light absorbed by a sample.

Question 20

Vibrational relaxation

Answer 20

A electron moves from a higher vibrational state back to its ground state. This happens before electronic relaxation.

Question 21

Stokes and anti-stokes

Answer 21

In the contextof Raman scattering: a photon hits a particle, and is scattered.

Stokes: the photon that is scattered has a lower energy

Anti-stokes: the photon scattered has higher energy

Question 22

Coherent Radiation

Answer 22

Phases of two or more waves representing the radiation differ by a known constant. Ex: laser radiation

Question 23

Superposition principal

Answer 23

waves of radiation can overlap. Think constructive/destructive interference

Question 24

Refractive index

Answer 24

The speed light travels through a medium compared to the speed of light in a vacuum.

n=c/v

n=refractive index
c=speed of light in a vacuum
v=velocity of radiation in the medium

Question 25

Normal dispersion

Answer 25

ratio of refractive index (n) to the wavelength of light (lambda)

Question 26

Anomalous dispersion

Answer 26

Incident radiation matches the natural harmonics of a molecule. Therefore absorbance occurs.

Question 27

work function

Answer 27

minimum energy needed to remove an electron t=from the surface of a substance.

Question 28

Photoelectric effect

Answer 28

photon in. Electron out.

Question 29

Ground state

Answer 29

lowest energy level

Question 30

electronic excitation

Answer 30

Electron excited to a higher energy state

Question 31

Fluorescence

Answer 31

• excited.
• loss of vibrational energy. (non-radiative decay meaning no light lost)
• emits lights back to ground state.

Question 32

phosphorescence

Answer 32

• excited
• decay with a spin flip(therefore takes much longer than fluorescence)
• light emitted. back to ground state

Question 33

stokes shift

Answer 33

emitting photon is less than the absorbed photon.